I wrote a Marine FAQ (Frequently asked questions) to hopefully help out some beginners...
Acronyms
General
ASW = Artificial Salt Water
BB = Barebottom (no substrate)
BR = Base Rock
BS = Baking Soda (sodium bicarbonate)
CC = Crushed Coral
CL = Closed Loop
CUC = Cleanup Crew
DI = Deionization
DOC = Dissolved Organic Carbon
DSB = Deep Sand Bed
EC = End Cap (light)
FO = Fish Only
FOWLR = Fish Only With Live Rock
for goodness sake = Favourite Fish Store
FTS = Full Tank Shot (photography)
HO = High Output (light)
HOB = Hang On Back
HOT = Hang On Tank
LFS = Local Fish Store
LNS = Low Nutrient System
LPS = Large Polyp Stony (coral)
LR = Live Rock
LS = Live Sand
MH = Metal Halide
NSW = Natural Salt Water
NO = Normal Output (light)
ORP = Oxygen Reduction Potential
PAR = Photosynthetically Active Radiation
PC = Power Compact (light)
PH = Powerhead
RSM = Red Sea Max (aquarium)
QT = Quarantine Tank
REDOX = Reduction / Oxidation
RO = Reverse Osmosis
RODI = Reverse Osmosis / Deionization
RTN = Rapid Tissue Necrosis (coral)
SB = Sandbed
SG = Specific Gravity
SPS = Small Polyp Stony (coral)
SSB = Shallow Sand Bed
STN = Slow Tissue Necrosis (coral)
TDS = Total Dissolved Solids
ULN = Ultra Low Nutrients
ULNS = Ultra Low Nutrient System
UV = Ultra Violet (light)
VHO = Very High Output (light)
WH = Wiring Harness (light)
WC = Water Change
Chemical
AC = Activated Carbon
KH = Alkalinity
CA = Calcium
GAC = Granular Activated Carbon
MG = Magnesium
PH = Acidity/Alkalinity measurement
PO4 = Phosphate
NH3 = Ammonia
NO2 = Nitrite
NO3 = Nitrate
Livestock
BS = Brittlestar
BTA = Bubgle Tip Anemone
CB = Coral Beauty
CBB = Copper Band Butterfly
CBS = Coral Banded Shrimp
GBTA = Green Bubble Tip Anemone
GSP = Green Star Polyps
LMB = Lawn Mower Blenny
LTA = Long Tentacle Anemone
PBT = Powder Blue Tang
RBTA = Rose Bulb Tip Anemone
What is...
What is a reef tank?
A reef tank is an enclosed ecosystem that simulates that of a real tropical reef. All organisms contained within it interact with each other in various ways; for example, to provide an environment (fish, corals), food (microorganisms), filtration (bacteria within live rock) or services (cleaner shrimps) Stability of the environment is maintained by a combination of sufficient lighting (for photosynthesis), water movement (for oxygenation, waste removal and providing food for corals) and the reef itself (for filtration and providing an environment for the tanks inhabitants)
What size tank should I buy?
There is no obvious answer to this so consider the following: (1) it only takes a small problem with a small tank to upset the entire ecosystem whereas the same size problem in a larger tank has a much lesser effect (2) marine fish require much more room than freshwater and most corals need sufficient space to grow so that they do not sting one another - so consider what you want to keep before you start and (3) a very large tank means more $$$ - not just the tank, it means more lighting, more powerful filtration equipment and more circulation, so factor this in your budget. However in general, perhaps the most common tank size is around 4 foot (300 litres)
What basic filtration equipment do I need to run a reef tank?
There are several different filtration methods in use. Perhaps the most common and recommended in practice today is the "berlin method". This method adopts the use of a protein skimming, plenty of live rock and strong lighting.
What ongoing maintenance is required?
Water changes are crucial. The amount you change may vary but typically 20% every 2 weeks is sufficient. Testing your water parameters frequently is also highly recommended. Once your tank is established, once every 2-4 weeks is sufficient although can vary depending on stocking levels. See the 'What test kits do I need?' section below.
What test kits do I need?
For the ongoing success of your reef tank, it is mandatory that you perform regular testing of your water parameters. The following test kits are required with recommendations on when and how often you should test (the frequency of testing will vary depending on your maintenance regime)
- Ammonia (during 'cycling')
- Nitrite (during 'cycling')
- Nitrate (during 'cycling' then every 4-8 weeks or more)
- Phosphate (every 1-2 months or when faced with unwanted algae problems *)
- Alkalinity (every 2-4 weeks)
- Calcium (every 2-4 weeks)
- Magnesium (every 2-4 weeks)
- pH (every 4 weeks or after a large water change)
- Salinity (every 4 weeks or after a large water change)
As you can see, there are a number of test kits you will need. Prices for these can vary from typically $25 - $50 each. Consider asking a fellow hobbyist if you can buy their test kit for use during the cycling stage. Also bear in mind that the majority of test kits have expiry dates so check before buying!
* - note that most phosphate kits do not measure low enough to get an accurate enough reading.
What is cycling?
Cycling (or technically "the nitrogen cycle") is the process in which your tank matures to a point where there is enough bacteria present to break down toxic ammonia to nitrite then finally to nitrate. It is essential you have a zero reading for ammonia (typically after about 2-4 weeks) and is recommended you have a zero reading for nitrite (typically after 4-6 weeks) before introducing any livestock (fish can tolerate nitrate readings up to about 20ppm) The entire cycling process can take anywhere from 30 to 90 days.
What is live rock?
Calcium carbonate skeletons of corals and other calcareous organisms colonised by beneficial bacteria and other marine organisms that live in porus holes in the rock. Live rock is beneficial as the anaerobic bacteria deep within the rock convert nitrate to free nitrogen gas, thus acting as biological filtration. It also provides a home for microorganisms and hiding places for fish.
What is a calcium reactor?
A device basically made up of a chamber containing calcium carbonate media. The chamber is injected (usually via a bubble counter) with CO2 gas which increases acidity (or decreases pH) causing the media to breakdown. The dissolved calcium carbonate is subsequently drip fed into your tank providing a continuous calcium supplement to your corals
What is a protein skimmer?
A device used to remove excess waste products from saltwater aquariums. Protein skimming (also known as "foam fractionation") is achieved by the device producing fine bubbles or "foam" which organic impurities are attached too. The "foam" is channeled out of the device and into a collection cup which can later be discarded.
What is kalkwasser?
Kalkwasser is German for "limewater" (or also known as calcium hydroxide) Kalk has a very high pH (around 12-12.5) It is usually dissolved with topoff water which is slowly drip-fed at night to help maintain pH and alkalinity levels and add inorganic Calcium to the aquarium. Add approximately 1 teaspoon of kalkwasser powder to 5 litres of water, mix well and dose slowly.
What is reverse osmosis?
Reverse Osmosis (RO) is a water purification process. It separates solids from water by applying pressure to water and forcing it through an RO membrane. One side of the membrane retains solute whilst pure water passes out the other side. In the reef keeping hobby, RO is often used with DI to produce highly pure water that is used as replacement water (from evaporation) Because of its high purity it adds no nutrients to the system thus reducing unwanted algae growth. RO typically reduces around 95% of impurities.
What is deionization?
Deionization (DI) is a water purification process. Water is passed slowly over ion exchange resin (typically small beads) attracting ions such as iron, copper, chloride, etc from the water. In the reef keeping hobby, DI is often used with RO to produce highly pure water that is used as replacement water (from evaporation) Because of its high purity it adds no nutrients to the system thus reducing unwanted algae growth. DI typically reduces around 99% of impurities.
What is phytoplankton?
Phytoplankton are microscopic floating plants, such as algae or diatoms that live suspended in bodies of water and that drift about because they cannot move by themselves or because they are too small or too weak to swim effectively against a current. Most phytoplankton are too small to be individually seen with the naked eye. Phytoplankton is fed upon by zooplankton such as copepods and amphipods.
What is zooplankton?
Zooplankton are the tiny animals that swim around in the water column. These small invertebrates are generally grouped into rotifers, cladocerans, and copepods. Zooplankton are part of the bottom of the aquatic food chain and typically feed upon phytoplankton and are typically fed upon themselves by fish and other aquatic life.
Back to top
Water Chemistry
Alkalinity
Alkalinity, or also known as the "buffering capacity", is a measure of the capacity of water to neutralize acids without a change in pH. It is primarily due to the presence of naturally available bicarbonate, carbonate, and hydroxide ions in the water. Alkalinity is measured in kH, mEq/L or ppm and should be maintained between 7-11kH (or 2.5-4.0meq/l or 125-200ppm CaCO3) You can use baking soda to raise Alkalinity (1tspn will raise 170 litres by 1kH)
Calcium
Calcium is one of the most essential elements in a reef tank. Corals build their skeletal structures from calcium carbonate extracted from seawater. Calcium is measured in ppm and should be maintained between 380–450ppm calcium ion (or 950-1125 ppm CaCO equivalents) Levels of calcium can be maintained by use of a Calcium Reactor (see above) dosing the required amount of Calcium Chloride Dihydrate (CaCl2), Kalkwasser or other alternatives. If mixing CaCl2 its solubility in water at 20°C is approx 75g per 100ml
Magnesium
Magnesium is the third most plentiful element dissolved in seawater and is about five times more abundant than calcium. It is an essential mineral involved in many biological processes in every living organism. Magnesium is measured in ppm and should be maintained between 1250-1350ppm. Levels of magnesium can be maintained by adding magnesium chips to a Calcium Reactor (see above) or dosing the required amount of Magnesium Chloride Hexahydrate (MgCl2) also known as "Magflake" (or other alternatives) If mixing MgCl2 its solubility in water at 20°C is approx 170g per 100ml of water
Nitrate
Nitrate (NO3) is an oxidized ion of nitrogen. Nitrifying bacteria can convert nitrite (NO2–) to nitrate in the nitrogen cycle. Nitrate can fuel undesirable algae growth so should be maintained as low as possible. Nitrate is measured in ppm and should be maintained between 0-5ppm in a reef tank (although is ok at slightly higher levels in a fish only aquarium)
Phosphate
Phosphate (PO4) is a compound of Phosphorus, a trace element naturally occuring in seawater although at extremely low levels (typcially 0.002ppm) Phosphate is considered an 'algae fertiliser' and it is the primary source for many forms of undesired algae (primarily hair algae) Phosphate is often introduced via unfiltered tap water, some forms of salt mix, calcium additives, activated carbon or kH buffers. Running kalkwasser can help reduce phosphate levels. Phosphate is measured in ppm and should be kept at 0.03 or less (or typically 'unmeasurable' on a reef hobbyist test kit)
pH
pH is a measure of the acidity or alkalinity of a solution. pH is measured on a scale of -5 (most acidic) to 14 (most alkaline) with 7 being neutral (neither acidic nor alkaline) In a reef tank pH should be maintained between 7.8-8.5, or more preferably between 8.1-8.3 To keep a stable pH, ensure the room your tank is in has adequate ventilation (leave some windows open) and the tank itself has sufficient water movement. Also consider running reverse lighting if you have a refugium.
Troubleshooting
My water is evaporating, what do I do?
It is completely normal for water in your tank to evaporate, one of the biggest contributors being heat from your lights (specifically halides). The most important thing to be aware of is that the replacement water MUST BE FRESH WATER! If you make the mistake of replacing evaporated water with saltwater, your salinity will increase to such levels that you will essentially "burn" your fish and corals.
I'm having problems with my coral, what do I do?
Unfortunately there is no single answer to this question. However, assuming you have an established tank the following are the most important things to check in the following order:
Salinity: Too high or too low will melt your corals. This is often the most common area where beginners fail. A refractometer is recommended for testing (and dont forget to top up evaporation with freshwater!) Aim for around 1.025.
Calcium/Alkalinity: Because of the uptake of these parameters by corals, its crucial that these levels are within the required range. Calcium should be kept between 380-450, Alkalinity typically from 7 to 11.
Flow: Corals require adequate water movement in order to wash away metabolic waste and more importantly, in aiding the mechanisms of respiration and photosynthesis. Water flow is too often underestimated in reef tanks. Aim for a minimum of 10 times turnover in your display, although 20 or more is preferred.
Placement: Corals are constantly in chemical warfare with one another, battling for space to grow. Most corals can 'sting' one another, some more aggressive than others so if there is localised damage, check any neighbouring corals. Some corals are able to send out 'sweepers' 6" or more; research your coral or provide ample room.
Lighting: Suitable lighting is required for (hermatypic) corals (or more specifically, zooxanthellae within the corals) for optimal photosynthesis. Remember different corals have different light requirements so research first to find the optimal placement.
Tank inhabitants: There are many types of fish unsuited to reef aquaria. Many angels for example have a tendency to nip at corals, clams or invertebrates. Check that all your livestock are well suited for a reef tank.
Coral Disease: See the FAQ Coral Disease section for more information on coral bleaching, STN/RTN, etc
Other: There are many other causes for corals looking damaged, unhealthy or dying. If you're still stumped, post a question under the Quarantine forum on the a bunch of sad old men who can't tell the difference between whitespot and a pod forums.
I'm getting bad algae growth, help?!
Welcome to reef keeping! Many tanks will go through an unwanted algae stage (quite commonly after cycling) until they reach full maturity. This will continue to occur until the Live Rock completely sheds any detritus stored in it (the leaching of this causes nitrates and phosphates, fueling the bad algae) What you need to achieve is a point where the good algae (eg: Coralline - the pink calcaerous algae) and corals, outcompete the bad algae for whatever nutrients remain in your tank. This however also requires that you have good Nutrient export (as the nutrient uptake by corals and Coralline is very low) You can achieve this by regular water changes or running phosphate removers, however arguably the most effective means of nutrient export is a good quality Protein Skimmer. Also ensure you are not adding nutrients by overfeeding, using tap water for top-up or having an overstocked tank. Lastly ensure you have appropriate lighting (one that promotes good coral growth, not unwanted algae growth) Tanks are likely to experience green hair algae, diatoms and cyanobacteria before reaching that equilibrium point. The time it takes to come right depends on how thorough and consistant you are with maintenance.
I'm getting poor coral growth, why?
Lack in coral growth is most commonly caused by low levels of calcium, alkalinity and pH. All of these parameters must be within there required range for optimal growth (refer to the sections above for appropriate levels) Phosphate can also inhibit coral growth as well as cause nuisance algae.
Unwanted Algae
I have a brown/golden dusting on my glass/rocks?
This is most likely to be Diatoms. Strong diatom growth is quite common after a new tank has finished cycling or when something new (rock, fish) is added to the tank. Diatoms feed off nutrients, so ensure mechanisms are in place to reduce nitrates, phosphates and DOC's - however Diatom growth is most responsive to Silicates (most often introduced through tapwater) so ensure you use filtered water for top off. As usual, ensure you also have appropriate lighting and flow.
I have a red slime coating my rocks/substrate?
This is most likely to be Cyanobacteria or "red slime" algae (there may also be the formation of small bubbles on the slime, the presence of these usually confirmation - the oxygen bubbles themselves a byproduct of the cyano). Phosphates, Nitrates and DOCs (dissolved organic compounds) are food sources for Cyano, so ensure mechanisms are in place to reduce these. Also ensure the tank has adequate ventilation, as CO2 is also a food source for algae. As usual, ensure you also have appropriate lighting and flow.
Coral Disease
What is bleaching?
Bleaching is when corals turn white, usually from the tips down (also see STN/RTN) The tissue is white, but still living, and is most often caused by excessive light. Bleaching can often be cured by reducing the intensity of the light and slowly reacclimatising the corals too it.
What is STN/RTN?
STN/RTN stands for Slow/Rapid Tissue Necrosis respectively; the prefix simply defining how quickly the necrosis occurs. STN/RTN is when a coral starts to bleach (turn white from dying tissue) usually from the base of the coral upwards. STN is often caused by the introduction of a new colony that becomes stressed. The stressed coral can often produce chemicals that produce extreme reactions in other corals. It is usually best to remove the offending colonies to a quarantine tank until they are over the stress of shipping. Water changes and carbon will help remove chemical messengers from the tank water. RTN is often caused by a sudden and large change in water parameters, be sure to double check before dosing any additives.
Acronyms
General
ASW = Artificial Salt Water
BB = Barebottom (no substrate)
BR = Base Rock
BS = Baking Soda (sodium bicarbonate)
CC = Crushed Coral
CL = Closed Loop
CUC = Cleanup Crew
DI = Deionization
DOC = Dissolved Organic Carbon
DSB = Deep Sand Bed
EC = End Cap (light)
FO = Fish Only
FOWLR = Fish Only With Live Rock
for goodness sake = Favourite Fish Store
FTS = Full Tank Shot (photography)
HO = High Output (light)
HOB = Hang On Back
HOT = Hang On Tank
LFS = Local Fish Store
LNS = Low Nutrient System
LPS = Large Polyp Stony (coral)
LR = Live Rock
LS = Live Sand
MH = Metal Halide
NSW = Natural Salt Water
NO = Normal Output (light)
ORP = Oxygen Reduction Potential
PAR = Photosynthetically Active Radiation
PC = Power Compact (light)
PH = Powerhead
RSM = Red Sea Max (aquarium)
QT = Quarantine Tank
REDOX = Reduction / Oxidation
RO = Reverse Osmosis
RODI = Reverse Osmosis / Deionization
RTN = Rapid Tissue Necrosis (coral)
SB = Sandbed
SG = Specific Gravity
SPS = Small Polyp Stony (coral)
SSB = Shallow Sand Bed
STN = Slow Tissue Necrosis (coral)
TDS = Total Dissolved Solids
ULN = Ultra Low Nutrients
ULNS = Ultra Low Nutrient System
UV = Ultra Violet (light)
VHO = Very High Output (light)
WH = Wiring Harness (light)
WC = Water Change
Chemical
AC = Activated Carbon
KH = Alkalinity
CA = Calcium
GAC = Granular Activated Carbon
MG = Magnesium
PH = Acidity/Alkalinity measurement
PO4 = Phosphate
NH3 = Ammonia
NO2 = Nitrite
NO3 = Nitrate
Livestock
BS = Brittlestar
BTA = Bubgle Tip Anemone
CB = Coral Beauty
CBB = Copper Band Butterfly
CBS = Coral Banded Shrimp
GBTA = Green Bubble Tip Anemone
GSP = Green Star Polyps
LMB = Lawn Mower Blenny
LTA = Long Tentacle Anemone
PBT = Powder Blue Tang
RBTA = Rose Bulb Tip Anemone
What is...
What is a reef tank?
A reef tank is an enclosed ecosystem that simulates that of a real tropical reef. All organisms contained within it interact with each other in various ways; for example, to provide an environment (fish, corals), food (microorganisms), filtration (bacteria within live rock) or services (cleaner shrimps) Stability of the environment is maintained by a combination of sufficient lighting (for photosynthesis), water movement (for oxygenation, waste removal and providing food for corals) and the reef itself (for filtration and providing an environment for the tanks inhabitants)
What size tank should I buy?
There is no obvious answer to this so consider the following: (1) it only takes a small problem with a small tank to upset the entire ecosystem whereas the same size problem in a larger tank has a much lesser effect (2) marine fish require much more room than freshwater and most corals need sufficient space to grow so that they do not sting one another - so consider what you want to keep before you start and (3) a very large tank means more $$$ - not just the tank, it means more lighting, more powerful filtration equipment and more circulation, so factor this in your budget. However in general, perhaps the most common tank size is around 4 foot (300 litres)
What basic filtration equipment do I need to run a reef tank?
There are several different filtration methods in use. Perhaps the most common and recommended in practice today is the "berlin method". This method adopts the use of a protein skimming, plenty of live rock and strong lighting.
What ongoing maintenance is required?
Water changes are crucial. The amount you change may vary but typically 20% every 2 weeks is sufficient. Testing your water parameters frequently is also highly recommended. Once your tank is established, once every 2-4 weeks is sufficient although can vary depending on stocking levels. See the 'What test kits do I need?' section below.
What test kits do I need?
For the ongoing success of your reef tank, it is mandatory that you perform regular testing of your water parameters. The following test kits are required with recommendations on when and how often you should test (the frequency of testing will vary depending on your maintenance regime)
- Ammonia (during 'cycling')
- Nitrite (during 'cycling')
- Nitrate (during 'cycling' then every 4-8 weeks or more)
- Phosphate (every 1-2 months or when faced with unwanted algae problems *)
- Alkalinity (every 2-4 weeks)
- Calcium (every 2-4 weeks)
- Magnesium (every 2-4 weeks)
- pH (every 4 weeks or after a large water change)
- Salinity (every 4 weeks or after a large water change)
As you can see, there are a number of test kits you will need. Prices for these can vary from typically $25 - $50 each. Consider asking a fellow hobbyist if you can buy their test kit for use during the cycling stage. Also bear in mind that the majority of test kits have expiry dates so check before buying!
* - note that most phosphate kits do not measure low enough to get an accurate enough reading.
What is cycling?
Cycling (or technically "the nitrogen cycle") is the process in which your tank matures to a point where there is enough bacteria present to break down toxic ammonia to nitrite then finally to nitrate. It is essential you have a zero reading for ammonia (typically after about 2-4 weeks) and is recommended you have a zero reading for nitrite (typically after 4-6 weeks) before introducing any livestock (fish can tolerate nitrate readings up to about 20ppm) The entire cycling process can take anywhere from 30 to 90 days.
What is live rock?
Calcium carbonate skeletons of corals and other calcareous organisms colonised by beneficial bacteria and other marine organisms that live in porus holes in the rock. Live rock is beneficial as the anaerobic bacteria deep within the rock convert nitrate to free nitrogen gas, thus acting as biological filtration. It also provides a home for microorganisms and hiding places for fish.
What is a calcium reactor?
A device basically made up of a chamber containing calcium carbonate media. The chamber is injected (usually via a bubble counter) with CO2 gas which increases acidity (or decreases pH) causing the media to breakdown. The dissolved calcium carbonate is subsequently drip fed into your tank providing a continuous calcium supplement to your corals
What is a protein skimmer?
A device used to remove excess waste products from saltwater aquariums. Protein skimming (also known as "foam fractionation") is achieved by the device producing fine bubbles or "foam" which organic impurities are attached too. The "foam" is channeled out of the device and into a collection cup which can later be discarded.
What is kalkwasser?
Kalkwasser is German for "limewater" (or also known as calcium hydroxide) Kalk has a very high pH (around 12-12.5) It is usually dissolved with topoff water which is slowly drip-fed at night to help maintain pH and alkalinity levels and add inorganic Calcium to the aquarium. Add approximately 1 teaspoon of kalkwasser powder to 5 litres of water, mix well and dose slowly.
What is reverse osmosis?
Reverse Osmosis (RO) is a water purification process. It separates solids from water by applying pressure to water and forcing it through an RO membrane. One side of the membrane retains solute whilst pure water passes out the other side. In the reef keeping hobby, RO is often used with DI to produce highly pure water that is used as replacement water (from evaporation) Because of its high purity it adds no nutrients to the system thus reducing unwanted algae growth. RO typically reduces around 95% of impurities.
What is deionization?
Deionization (DI) is a water purification process. Water is passed slowly over ion exchange resin (typically small beads) attracting ions such as iron, copper, chloride, etc from the water. In the reef keeping hobby, DI is often used with RO to produce highly pure water that is used as replacement water (from evaporation) Because of its high purity it adds no nutrients to the system thus reducing unwanted algae growth. DI typically reduces around 99% of impurities.
What is phytoplankton?
Phytoplankton are microscopic floating plants, such as algae or diatoms that live suspended in bodies of water and that drift about because they cannot move by themselves or because they are too small or too weak to swim effectively against a current. Most phytoplankton are too small to be individually seen with the naked eye. Phytoplankton is fed upon by zooplankton such as copepods and amphipods.
What is zooplankton?
Zooplankton are the tiny animals that swim around in the water column. These small invertebrates are generally grouped into rotifers, cladocerans, and copepods. Zooplankton are part of the bottom of the aquatic food chain and typically feed upon phytoplankton and are typically fed upon themselves by fish and other aquatic life.
Back to top
Water Chemistry
Alkalinity
Alkalinity, or also known as the "buffering capacity", is a measure of the capacity of water to neutralize acids without a change in pH. It is primarily due to the presence of naturally available bicarbonate, carbonate, and hydroxide ions in the water. Alkalinity is measured in kH, mEq/L or ppm and should be maintained between 7-11kH (or 2.5-4.0meq/l or 125-200ppm CaCO3) You can use baking soda to raise Alkalinity (1tspn will raise 170 litres by 1kH)
Calcium
Calcium is one of the most essential elements in a reef tank. Corals build their skeletal structures from calcium carbonate extracted from seawater. Calcium is measured in ppm and should be maintained between 380–450ppm calcium ion (or 950-1125 ppm CaCO equivalents) Levels of calcium can be maintained by use of a Calcium Reactor (see above) dosing the required amount of Calcium Chloride Dihydrate (CaCl2), Kalkwasser or other alternatives. If mixing CaCl2 its solubility in water at 20°C is approx 75g per 100ml
Magnesium
Magnesium is the third most plentiful element dissolved in seawater and is about five times more abundant than calcium. It is an essential mineral involved in many biological processes in every living organism. Magnesium is measured in ppm and should be maintained between 1250-1350ppm. Levels of magnesium can be maintained by adding magnesium chips to a Calcium Reactor (see above) or dosing the required amount of Magnesium Chloride Hexahydrate (MgCl2) also known as "Magflake" (or other alternatives) If mixing MgCl2 its solubility in water at 20°C is approx 170g per 100ml of water
Nitrate
Nitrate (NO3) is an oxidized ion of nitrogen. Nitrifying bacteria can convert nitrite (NO2–) to nitrate in the nitrogen cycle. Nitrate can fuel undesirable algae growth so should be maintained as low as possible. Nitrate is measured in ppm and should be maintained between 0-5ppm in a reef tank (although is ok at slightly higher levels in a fish only aquarium)
Phosphate
Phosphate (PO4) is a compound of Phosphorus, a trace element naturally occuring in seawater although at extremely low levels (typcially 0.002ppm) Phosphate is considered an 'algae fertiliser' and it is the primary source for many forms of undesired algae (primarily hair algae) Phosphate is often introduced via unfiltered tap water, some forms of salt mix, calcium additives, activated carbon or kH buffers. Running kalkwasser can help reduce phosphate levels. Phosphate is measured in ppm and should be kept at 0.03 or less (or typically 'unmeasurable' on a reef hobbyist test kit)
pH
pH is a measure of the acidity or alkalinity of a solution. pH is measured on a scale of -5 (most acidic) to 14 (most alkaline) with 7 being neutral (neither acidic nor alkaline) In a reef tank pH should be maintained between 7.8-8.5, or more preferably between 8.1-8.3 To keep a stable pH, ensure the room your tank is in has adequate ventilation (leave some windows open) and the tank itself has sufficient water movement. Also consider running reverse lighting if you have a refugium.
Troubleshooting
My water is evaporating, what do I do?
It is completely normal for water in your tank to evaporate, one of the biggest contributors being heat from your lights (specifically halides). The most important thing to be aware of is that the replacement water MUST BE FRESH WATER! If you make the mistake of replacing evaporated water with saltwater, your salinity will increase to such levels that you will essentially "burn" your fish and corals.
I'm having problems with my coral, what do I do?
Unfortunately there is no single answer to this question. However, assuming you have an established tank the following are the most important things to check in the following order:
Salinity: Too high or too low will melt your corals. This is often the most common area where beginners fail. A refractometer is recommended for testing (and dont forget to top up evaporation with freshwater!) Aim for around 1.025.
Calcium/Alkalinity: Because of the uptake of these parameters by corals, its crucial that these levels are within the required range. Calcium should be kept between 380-450, Alkalinity typically from 7 to 11.
Flow: Corals require adequate water movement in order to wash away metabolic waste and more importantly, in aiding the mechanisms of respiration and photosynthesis. Water flow is too often underestimated in reef tanks. Aim for a minimum of 10 times turnover in your display, although 20 or more is preferred.
Placement: Corals are constantly in chemical warfare with one another, battling for space to grow. Most corals can 'sting' one another, some more aggressive than others so if there is localised damage, check any neighbouring corals. Some corals are able to send out 'sweepers' 6" or more; research your coral or provide ample room.
Lighting: Suitable lighting is required for (hermatypic) corals (or more specifically, zooxanthellae within the corals) for optimal photosynthesis. Remember different corals have different light requirements so research first to find the optimal placement.
Tank inhabitants: There are many types of fish unsuited to reef aquaria. Many angels for example have a tendency to nip at corals, clams or invertebrates. Check that all your livestock are well suited for a reef tank.
Coral Disease: See the FAQ Coral Disease section for more information on coral bleaching, STN/RTN, etc
Other: There are many other causes for corals looking damaged, unhealthy or dying. If you're still stumped, post a question under the Quarantine forum on the a bunch of sad old men who can't tell the difference between whitespot and a pod forums.
I'm getting bad algae growth, help?!
Welcome to reef keeping! Many tanks will go through an unwanted algae stage (quite commonly after cycling) until they reach full maturity. This will continue to occur until the Live Rock completely sheds any detritus stored in it (the leaching of this causes nitrates and phosphates, fueling the bad algae) What you need to achieve is a point where the good algae (eg: Coralline - the pink calcaerous algae) and corals, outcompete the bad algae for whatever nutrients remain in your tank. This however also requires that you have good Nutrient export (as the nutrient uptake by corals and Coralline is very low) You can achieve this by regular water changes or running phosphate removers, however arguably the most effective means of nutrient export is a good quality Protein Skimmer. Also ensure you are not adding nutrients by overfeeding, using tap water for top-up or having an overstocked tank. Lastly ensure you have appropriate lighting (one that promotes good coral growth, not unwanted algae growth) Tanks are likely to experience green hair algae, diatoms and cyanobacteria before reaching that equilibrium point. The time it takes to come right depends on how thorough and consistant you are with maintenance.
I'm getting poor coral growth, why?
Lack in coral growth is most commonly caused by low levels of calcium, alkalinity and pH. All of these parameters must be within there required range for optimal growth (refer to the sections above for appropriate levels) Phosphate can also inhibit coral growth as well as cause nuisance algae.
Unwanted Algae
I have a brown/golden dusting on my glass/rocks?
This is most likely to be Diatoms. Strong diatom growth is quite common after a new tank has finished cycling or when something new (rock, fish) is added to the tank. Diatoms feed off nutrients, so ensure mechanisms are in place to reduce nitrates, phosphates and DOC's - however Diatom growth is most responsive to Silicates (most often introduced through tapwater) so ensure you use filtered water for top off. As usual, ensure you also have appropriate lighting and flow.
I have a red slime coating my rocks/substrate?
This is most likely to be Cyanobacteria or "red slime" algae (there may also be the formation of small bubbles on the slime, the presence of these usually confirmation - the oxygen bubbles themselves a byproduct of the cyano). Phosphates, Nitrates and DOCs (dissolved organic compounds) are food sources for Cyano, so ensure mechanisms are in place to reduce these. Also ensure the tank has adequate ventilation, as CO2 is also a food source for algae. As usual, ensure you also have appropriate lighting and flow.
Coral Disease
What is bleaching?
Bleaching is when corals turn white, usually from the tips down (also see STN/RTN) The tissue is white, but still living, and is most often caused by excessive light. Bleaching can often be cured by reducing the intensity of the light and slowly reacclimatising the corals too it.
What is STN/RTN?
STN/RTN stands for Slow/Rapid Tissue Necrosis respectively; the prefix simply defining how quickly the necrosis occurs. STN/RTN is when a coral starts to bleach (turn white from dying tissue) usually from the base of the coral upwards. STN is often caused by the introduction of a new colony that becomes stressed. The stressed coral can often produce chemicals that produce extreme reactions in other corals. It is usually best to remove the offending colonies to a quarantine tank until they are over the stress of shipping. Water changes and carbon will help remove chemical messengers from the tank water. RTN is often caused by a sudden and large change in water parameters, be sure to double check before dosing any additives.
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