Fish Nutrition.

Compiled from articles written by our members.

FNZAS Fish nutrition notes.pdf

FNZAS Fish nutrition notes

What should I feed my tropical fish?

Author: Adrienne Dodge

First published in Aquarium World August 2013

This is a question that commonly pops up.  What you feed your fish is as important as the aquarium conditions you provide for them. For newer fish keepers I have placed a table at the bottom of this article giving some idea of the basic foods to feed the type of fish typically kept by beginners to the hobby.

The type of food you feed your fish depends largely on the following   

- The size of your fish and the size of its mouth                                                                                                          

- Whether your fish is a herbivore (eats plants), a carnivore (eats animals), or an omnivore (eats both)                                                           - Is your fish a surface feeder or a bottom feeder?                                                                                                      

- Does your fish feed during the day or at night only?     

It is important to remember that regardless of what type of food you feed to your fish, varying the diet to ensure balanced nutrition is also necessary. There are a huge number of commercially prepared fish foods available that can be used. A lot will depend on your preference and how convenient it is for you to feed it. A combination of dry as well as frozen and fresh/live foods will ensure a well-balanced diet.

Dry foods come as pellets, flakes, wafers and sticks. Formulations for herbivores, omnivores and carnivores are easily obtainable in your local fish/pet shops (LFS), as is fish specific food ie food for bettas, goldfish, cichlids, arowana. Most foods available range in size from tiny pellets for fish with small mouths, to large sticks for the bigger predatory fish like Oscars or Jaguar Cichlids.

Each food type has its pros and cons – sinking wafers are great for catfish but no good for surface feeders ie Hatchet fish, Pantadon Butterfly Fish. Flakes can be crushed or crumbled for smaller fish like Guppies and Neon Tetras but will not sustain large bodied fish as they do not contain enough bulk. Likewise large pellets are too big for fish with tiny mouths such as Mosquito Rasbora, or narrow throats such as the Rainbowfish species. Some pellets will float for a while before slowly sinking, often making these the preferred food for a community tank.

The majority of frozen or freeze dried foods are processed organisms like brine shrimp or bloodworms. Some people believe that freeze-drying food retains more vitamins than freezing but both result in some loss of nutrition. Most fish prefer frozen foods over freeze-dried but freeze-dried are more easily crumbled for smaller fish. Commonly available freeze-dried foods found in NZ are tubifex, bloodworms, daphnia and de-capsulated brine shrimp. Brine shrimp, bloodworms, daphnia and mysis shrimp are some of the frozen foods available from your LFS.

Most fish enjoy live foods. Foods like microworms, whiteworms and blackworms are easily cultured at home. Daphnia can be found in water troughs and ponds exposed to the sun while mosquito lavae can easily be cultured by leaving a bucket of water, with a handful of grass added, out for the mosquitoes to lay their eggs in.  Larger predators will also enjoy worms and crickets. More experienced fish keepers and breeders also hatch bbs (baby brine shrimp) for feeding to their newly hatched fry or grow-out tanks.

Beginning fish keepers – the majority of new fish keepers tend to start off by purchasing fish such as guppies, neons, and the danio species (all small tropical fish), or mountain minnows (coldwater fish). Another fish, which is popular with new fish keepers is the dwarf gourami. Bristlenose catfish and corydora (cory) are also fish commonly purchased by new fishkeepers.  You will note that there are blanched vegetables listed below for some fish – vege clips can be purchased from LFS, for around $11, to hold these and prevent them from floating around the tank.

Goldfish are a cold water fish which new fish keepers often purchase.  The type of goldfish you buy largely determines what sort of food you should feed it, as does whether or not it is to be kept in a pond or a tank.  I will just cover food for a goldfish in a tank.

If you have a goldfish like a Comet or a Shubunkin, which are the original shaped goldfish, then a high quality flake or sinking pellet food will be good for them.  Lower quality will cloud your tank water quickly.  However if you purchase a fish like a Blackmoor, Oranda, or any fancy goldfish for that matter, you are better to feed them a sinking pellet food.  The reason for this is that the swim bladder in fancy goldfish is packed in tightly and when they come up to eat flake foods it is common for them to suck in air while eating.  The location of the swim bladder makes it very difficult for this air to be released.

“In terms of fish food, variety truly is the spice of life. Just keep it fresh and feed it lightly." ~Ted Dengler Coletti

 As you can see there are a wide variety of species that can be kept and therefore just as wide a variety of foods necessary for their ongoing health, research is your biggest aid before purchasing fish to ensure you can meet their dietary needs. There are many good quality foods available commercially with many targeted for different species specific nutritional requirements, most fish can be categorised for diet as either carnivores (meat eaters), Omnivores (eat both meat and vegetation) and herbivores (eat mainly vegetable matter) so a good understanding of their diet in the wild is a must.

Herbivores tend to graze continuously which is why they are generally kept as algae eaters in aquaria so the high protein diet of carnivorous fish can lead to bloat issues with them, they ingest minute animals and bacteria while grazing but their digestive system can handle that, foods such as algae wafers are available but Slices of cucumber or blanched silverbeet can be offered also

Carnivores are adapted to digesting high protein foods so feed less frequently in the wild where insects, invertebrates and even with larger species terrestrial animals may be consumed and digested over a period of days.  Again there are many commercial foods available, a more natural option for many aquarists is offering Bloodworms, worms ,insects,  brine shrimp, fish and chicken or ox heart, care must be taken with the heart option to remove any fat as mammalian fats are harder to digest for them. The diet of protein means that it is very easy for these types of fish to overfeed and cause health problems for them, obesity and fatty liver syndrome.

Omnivores eat both plant and animal matter but generally will eat more protein based foods than plants

Different species of fish swim and feed in different areas of the water column in their natural habitat some feed on the bottom, mid water or are surface feeders while a few only feed at night so food should be appropriate for the species you keep, commercial foods available now are designed to target these feeding strategies.

For bottom feeders and grazing fish sinking foods and algae wafers are now produced, these fish generally have downward facing mouths usually with sensory organs such as whiskers or barbells around the mouth to help find food in murky conditions. Any food fed to the tank can be consumed by surface and mid water feeders so you need to ensure food is available for them to avoid them starving.

Grazing fish feed on algaes and bacteria that grow on plants , wood, rockwork and the insides of the aquarium so supplementing their food is a must in a well maintained system, species such as Panaques feed on Periphyton (a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus) that is attached to submerged surfaces in most aquatic ecosystems. Their specialised suckermouths are used to rasp this off wood and rocks in the environment, some native peoples refer to them as “Canoe eaters”

Surface feeders usually have upturned mouths and eyes high on their heads to aid their style of feeding, Arowanas, hatchet fish are good examples that feed on insects or animals near or have fallen onto the water surface.  This type of fish are good jumpers and need tight fitting lids on the aquarium, foods for these need a high protein content and are usually more buoyant in water

Mid water fish generally take their food from this part of the water column and comprise the largest group generally kept in captivity, natural foods include insects, crustaceans and other fish, so again high protein is a staple part of the diet.

Another thing to consider is that while most fish feed during daylight hours some are almost entirely nocturnal feeders and can miss out on food fed out during the day, the best strategy when housing these is to wait until the lights have gone out on the tank then feed out allowing them a food source when they are most active.

As has been mentioned there are many commercially made foods on the market and quality and nutritional value can vary greatly with them, early commercially prepared foods were very basic but nowadays a lot more science is involved in producing them. Fish food has been of low priority in the pet food market but going with trusted brands should ensure some quality in your choices, basically treat it like buying food for your personal use, check ingredients and don’t just purchase the one with the best looking label that has been designed to catch your eye .Again the type of food to feed depends on the requirements of particular species you are feeding, I will try to outline some of the basics below.

Though basically most fish foods contain similar ingredients we need to look for

Absence of toxic or potentially toxic ingredients

Absence of artificial colouring

Aquatic Animal protein and Preferred Plant Proteins as the primary protein sources

A fully nutritious food to include necessary vitamins and minerals with natural sources of vitamins and minerals being preferred.

Inclusion of the “Whole Fish”, or “Whole Krill” (in meal form or not) is preferred over fish meal or krill meal.

Try to avoid any food that utilizes Ethoxyquin, BHA, or BHT as preservatives, artificial colours and Menadione Sodium Bisulfite (Synthetic Vitamin K, aka K3) as these lower the quality of the food in approximating a natural diet.

A good site for reviews of brands of fish food https://fishtankadvisor.com/best-fish-food-reviews/

Types of food

Pellet foods, floating and sinking

Suitable for surface, bottom and some mid water species, the floating type is aerated during production for buoyancy, available in .5mm size for smaller species such as Guppies  to a 30mm plus protein enriched pellet for Arowana or large Catfish species.  Be careful as some basic pellet foods are high in phosphates and capable of polluting your system quickly.

Analysis of a good quality goldfish pellet:

Protein:                 38%

Fibre:                    2.55%

Fat:                        6%

Ash:                      4.36%

Calcium:               1.01%

Phosphate:          0.93%

Moisture:              10%

Usual Ingredients of a good quality goldfish pellet:

Anchovy Fish, Wheat Germ, Whole Wheat, Alfalfa, Hydrolyzed Protein Meal, Soy Meal, Gluten Protein, Spirulina, Marine Fish Oil, Vitamins (C- Stabilized, A, D, E, K, B1, B2, B6, Choline- chlorine, Niacin, Biotin, Folic Acid, B12), Minerals (Zinc Sulfate, Manganese Sulfate, Copper Sulfate, Potassium Sorbate, Di-calcium Phosphate), Additional Carotenoids (A-Xan, Cantha Xan, Xan-Yellow), All Essential Amino Acids, & Aqua Health's Aquagen Biogenic Performance Enhancer.

Hikari Massivore Pellet Ingredients

Fish meal, krill meal, starch, fish oil, wheat flour, dried seaweed meal, spirulina, brewer's dried yeast, dried Aspergillus niger fermentation extract, astaxanthin, canthaxanthin, DL-methionine, L-lysine, Vitamin A oil, Vitamin D3 supplement, Vitamin E supplement, menadione sodium bisulfite complex (source of Vitamin K), choline chloride, L-ascorbyl-2-polyphosphate (stabilized Vitamin C), inositol, calcium pantothenate, riboflavin, thiamine mononitrate, pyridoxine hydrochloride, niacin, folic acid, biotin, vitamin B12 supplement, ferrous sulfate, magnesium sulfate, zinc sulfate, manganese sulfate, cobalt sulfate, copper sulfate calcium iodate.

Flake Food

This is the most widely used food for ornamental fish  but has a limited shelf life once opened as it can deteriorate quicker than pelletised food as it is baked to remove moisture, it is consumed  by a wide variety of smaller tropical and saltwater fish and invertebrates. It is ideally suited to top dwellers and mid-water fish though numerous bottom dwelling species consume flake food once it has settled on the bottom. Quality flake food contains the same ingredients as pellets and floats until it takes on water then it slowly sinks to the bottom.

Algae Discs and Tablets

These are also available and formulated for herbivorous fish such as Plecostomus, Catfish and Chinese Algae Eaters and contain a large amount of Spirulina and vegetable matter, most are a sinking food that will settle on the substrate where they are available for those types of fish to access.

Freeze-dried

Freeze-dried foods mainly tubifex worms, bloodworms, Daphnia, Cyclops, Krill and Brine Shrimp are commercially available and can be offered as part of a varied diet. They are usually natural foods put through a freeze drying process to preserve most of their nutrients.

Commercial Fry Foods

These are available and usually come in a liquid or powder form with instructions for use on the label just be careful of overfeeding polluting te tank water.

Colour Enhancing Foods

These are available in most ranges of prepared fish foods, most use beta-carotene or other natural ingredients to bring out the colours of the fish. It can take 2 or 3 weeks for enhanced colour to start showing on your fish.

Low Phosphate Foods

These foods are manufactured to be highly digestible, resulting in less waste product to pollute the aquarium. Foods with low levels of phosphate means that there will be less algae, as phosphate encourages algae growth in an aquarium.

Typical % analysis of a low phosphate aquarium tropical fish food.

Crude Protein 44, Crude Fibre 2, Crude Fat 5, Moisture 8, Phosphorus 0.9, Ash 9.

Typical % analysis of a low phosphate goldfish food

Crude Protein 33,  Crude Fibre 2,  Crude Fat 5, Moisture 8,  Phosphorus 0.6,  Ash  8.

Frozen fish food

Many aquarists don’t bother to go to the trouble that culturing or collecting live food entails and so frozen foods are a very good alternative. Bloodworms, Daphnia, or brine shrimp may be found frozen in most pet stores this is done to preserve them and are usually sold in blister packs. Other mixes of blended natural foods can be found frozen in resealable bags with ingredients to suit different types of fish or turtles. Care should be taken when feeding these out as they can be very high in phosphates especially if thawed then refrozen often, which can cause algae problems in the system.

Live foods

Live food can include earthworms, daphnia, bloodworms, Mysid or Brine shrimp and feeder fish whereas young fry or larvae will need infusoria, newly hatched brine shrimp and microworms. These need to be either collected from the wild or cultured, culturing them ensures the risk of parasites is greatly reduced. Culturing methods for some popular types are listed below.

Mealworms

Meal worms are the larval stage of a black beetle (Tenebrio molitor) that is considered a pest as it infests grain storage facilities, they are used to feed fish, reptiles, birds, and small insectivorous animals. Culturing them is reasonably easy and inexpensive to do and just requires a plastic container that is not airtight, cardboard or polystyrene boxes are no good as the worms will chew through them. Half fill the container with Bran and place a small culture of mealworms on top of the bran, add a couple of slices of carrot and cover with a piece of cloth or a folded up sheet of newspaper. Larvae will accumulate in the paper or clot and make them easier to collect. Keep the box warm around 20-25°C is ideal but room temperature is adequate, cooler than that they slow down whereas if they too warm they become sterile. Do not allow the culture to get damp as it will sour the bran and kill off the worms, when feeding out remember the larger the worm generally the harder its outside surface is.

Brine Shrimp.

Artemia Culture:

Use a clear two litre soft drink bottle with the cap still attached, wash bottle to remove all drink residue.

The bottom can be cut off the bottle then a 4mm hole drilled in the cap and a length of airline siliconed into the cap.

I use another bottle cut at halfway to support the first bottle inverted in it then fix airline to valve then to the air pump, a one way valve can be put inline to prevent any backflow of water to pump.

Put 1 litre of NSW (Natural Salt Water) or 1 litre of fresh water with four tablespoons of sea salt added to it, or 2tablespoons and 1/2 teaspoon of baking soda then add 6–8 grams of Artemia cysts, and start gentle bubbles flowing. After 24 hours they should be ready to harvest,

I do this by turning the air off and letting them settle, once settled I remove airline from the valve and let this run into a collection cup. Strain the nauplii through a brine shrimp net, rinse with clean salt water and feed out immediately.

Filters:

Some people use air powered sponge filters but they need cleaning in fresh salt water 1 to 2 times weekly as they can be fouled by Artemia naupulii quite quickly, the small plastic Bio-filters can be used and coral rubble can be used for bio-media as these do not need cleaning as regularly.

 Various hydroids and other "pests" can show up, (mainly in the brood aquariums) and need to be removed by stripping down that tank. At the very least, these hydroids compete with the Mysids for food, and at the worst, they may actually consume juvenile fry.

White worms

Author: Barrie McKoy

For Killifish these have to be one of the easiest live foods to feed to growing fry and adults alike.
The worms themselves are a size that is halfway in-between both White Worms and Micro Worms. They will stay alive in the tanks for up to 48 hours which is great if you’re taking eggs from your fish and are going away for a few days.
I feed Grindals to fry that are about 15 to 20mm long with even those that are only 10mm getting the odd one or two.
I was shown this method by Matt Carter and have changed only the food I feed them to Luncheon Sausage.

Firstly you need a container to hold the worms; this should have a lid but needs to allow air in, in other words, holes drilled in the top. I’ve used a “click it” container.

This is placed in another container. In this case I’ve used an ice cream container to help keep the culture darker. When the Ice Cream lid goes on, I leave one corner open slightly to allow air in and out.

I use soil/peat from a small garden in the front of my garage. It has been built up over the last 30 years with top soil and peat from pot plants as well as a few grass clippings.

I fill the click it container about half full with this medium and dampen slightly so that the worms don’t simply dry out.

I add a starter culture of as many worms as I can realistically find without destroying my original culture and place a small amount of lunchon sausage on the top.

Just enough for them to eat over a two day period. I change this with fresh luncheon every two days and wait until the worms are multiplying quickly.

They will be clearly seen on the glass. And can be washed into your tanks to be eagerly consumed by your fish.
It’s enough to make you feel hungry isn’t it?

Barrie McKoy with special thanks to Matt Carter.
©This item may not be reproduced without written permission

Breeding Daphnia

Author: Caryl Simpson
First published in Aquarium World August 2006

Despite being commonly known as water fleas, daphnia are not fleas – or insects for that matter. They are crustaceans. Less than 3mm, they are the most common crustacean found in lakes, ponds and small streams. An important part of the food chain, daphnia harvest algae cells that convert sun energy into food then pass this energy on to other animals, like fish.

 Daphnia swim in a jerky manner by thrusting their powerful 2nd antennae forwards. This moves it towards the surface. It then pauses for a short while before the next stroke, slowly falling downwards again before the next stroke propels it forward again.

Breeding your own daphnia outside is a great way to get good, free food for your fishes. They are also good for clearing green water (but only if no fish are present as they will eat the daphnia before the daphnia get the chance to eat the algae).

Finding live cultures can be difficult so try to find an aquarist with a culture they are willing to share. I have found daphnia do not travel well, probably due to lack of oxygen. Visit a nearby farm and look in stock troughs, always a good source of daphnia. Watch you don’t get parasites, predators, or other nasties in with them too like blanket weed.

You will need a container in which they can breed. I use fibreglass ponds, a bath, and half a mussel float for mine. Larger containers are better as they keep a more constant temperature in summer. A good surface area is ideal as daphnia, although not demanding, appreciate a good oxygen supply. I am lucky where I live as I just fill my container with water and wait. The daphnia seem to find their own way into the container, along with other creatures like mosquito larvae.

Once you have your container, fill it with green water and add the daphnia. They will live and breed in this. You will find the water clears very quickly as the daphnia feast on the algae so you will need to feed the daphnia to keep them alive and breeding in large enough numbers to feed regularly to your fish. Green water and activated yeast are the best foods. About 5g of yeast per 10 litres every 5 days is sufficient.

Bacteria found in dried sheep, horse or cow dung is another food source. Put it in a nylon bag and hang in the container. The water will turn cloudy after a time which is the bacteria multiplying. A fast way to culture bacteria is to throw in some trout pellets or dog biscuits.

Other foods suggested are dried blood, blood meal, bran, wheat flour and sweet potato baby food mix. Try them out and see which suits you best. DO NOT OVERFEED, it will just foul the water. Experiment as amounts vary depending on the size of the container and the number of daphnia present.

To harvest the daphnia, and it is important to do this at least once a week to keep numbers in check, catch them with a fine net.

Make sure pesticides are not used anywhere your daphnia containers.

Lumbriculus variegatus - Blackworms

Author: Simon Check
First published in Aquarium World Aug 2011

Few fish can resist a wriggling worm as part of their diet. Blackworms are ideal live foods for your fish for the fact that the worms are easy to grow and will survive almost indefinitely in your tank until eaten, thus preventing pollution due to decomposition.

Although not bred or found often in New Zealand, Lumbriculus worms are actually quite common. They resemble Tubifex worms in appearance but this species of worms live in shallow water marshes, ponds, and swamps, feeding on microorganisms and organic material, unlike tubifex which prefer deeper less sanitary conditions. Reproduction is by division of the worms many (up to 150-200) segments, where each segment is able to develop into a fully functional individual. Sexual reproduction does occur, but is not very common. They can reach to approx 10cm in length when fully extended.

Lumbriculus uses its head to forage in sediments and debris, while its tail end, specialized for gas exchange, often projects upwards, When disturbed they will quickly contract itself into the sediment or swim away in a corkscrew fashion.

Photo: Simon Check

Breeding Blackworms

First task here is to acquire some blackworms. You can either ask other fish keepers if they can spare a few or you can search for some yourself. The most common way to find them is in the sediment or gravel in the bottom of Garden ponds. The image above is of an abundance of blackworms living in a Trout rearing pond (the supply of food for the worms is in abundance due to the public feeding of trout at the viewing window). Most ponds and or streams/ditches have blackworms, you just need to find them. Favourite micro habitats include layers of decomposing leaves, submerged rotting logs, or sediments at the base of emergent vegetation

To breed these worms all you need is a small glass tank or container (glass so you can view from the side), an air pump and air powered filter, Turkey baster/Syringe, some gravel and clean chlorine free water.

My setup is just a basic 20 X 20 X 20 cube tank, with a few cm of gravel. A cheap air powered sponge filter to keep the waste levels down is situated in the middle of the tank and the worms are simply introduced. There is conflicting information about as to the temperature that the tank should be kept at, but for best results I keep mine around 18 degrees Celsius. The worms will certainly survive much cooler temps but growth rates are dramatically reduced with the reduced temperatures. Simply add the gravel and half fill the tank with chlorine free water. Introduce the worms and add a small bit of decaying leaves and leave them for a day or two before feeding. This addition of the decaying leaves initially and after water changes in my experience has resulted in the reproduction rate initially increasing faster than without. I do not feed for the first day as I allow the worms to acclimatise to the changes and avoid polluting the tank.

Feeding is simple. I feed mine fish food (a handy use for that cheap supermarket fish flake that the mother in law gave you for Christmas). I just sprinkle a pinch in every few days and do not feed again until I cannot see the flake on the bottom. The worms live in the gravel and they can be seen congregating around the fish food.

Maintenance is minimal and involves just water changes and if the culturing is going well they will eventually require a full clean out as they produce a fair amount of waste which will foul the water. Simply gravel vac the tank into a bucket and don’t worry about sucking up the worms. You retrieve them from the bucket once the contents of the syphoned bucket is settled using a turkey baster or large syringe. The worms will just bunch up into a ball and are easy picking. Rinse them with fresh water and feed out half of them and then replace the remaining half in the worm tank.

Collection of worms to feed out between tank cleanups is as simple as stirring the gravel up and using a turkey baster/syringe to suck the worms up as they wriggle about in the water. Most fish will snap these up before they can escape. Apisto’s and Corydora love them. My Geophagus love them. Haven’t had a fish that doesn’t yet.

Collected worms ready for feeding out.

Photo: Simon Check

Infusoria

in the aquarium trade Infusoria is used to describe all kinds of microscopic aquatic organisms, both plant and animal. Infusoria are much smaller than brine shrimp nauplii so they are the perfect food for fry that have just hatched and have absorbed their yolk sac.  

The easiest way to culture infusoria is by cleaning out a glass or clear plastic jar, next fill the jar with water from an established aquarium, water from planted tanks is best. Once you have filled the jar, add some type of vegetable matter such as a small leaf of lettuce, a piece of potato or mulm/detritus from an active filter.  Then place the jar in sunlight on a windowsill works well, after a few days the jar will become cloudy or green which is the infusoria and they are ready to harvest.

The easiest way to harvest infusoria is to use an eye dropper or turkey baster to collect a small amount of water from the top of the culture jar and to squirt it directly into the fry tank at least twice a day so they will grow quickly.

Earthworms

Earthworms make a great fish food for larger fish and can be chopped up for smaller fish, you need to clean the worms by placing in moist sphagnum moss for a day or two before feeding out to allow them to clean their gut out as they can  cloud up the water.

                                                            Remember QUALITY & VARIETY is important in any animal’s diet.

Feed only as much as will be consumed immediately and no more!

Any leftovers will accumulate, decompose and eventually pollute the aquarium.