Robert Smith

Giardia's not nice, but there are worse. Look out for other nasties like drug resistant Salmonella. There have been a number of studies, most recently here in Oz about Salmonella in aquaria. About 10% are contaminated. Do not drink your fishtank water! I don't even let the syphon tube touch my mouth (I use my closed fist to form a bridge). Wash your hands after immersing them in the tank. Clean sinks used to dump tank water or wash bits of your tank with disinfectant/bleach.

Lady-Lene, NaOH is caustic (thus "caustic soda") but it you soak the wood in the NaOH to kill/remove the 'whatever' then soak it for a while in water any excess NaOH should be removed. Even if some gets absorbed into the wood and is released over time, if you can't detect a change in teh pH of your tank then there is no problem.

I just dropped these equations into the Technical forum with a more descriptive title

There's a thread running in the Freshwater section that is getting a bit technical. It seems the summary is that fans are the best method of cooling largish tanks, especially over days or longer. For small tanks or to compensate for short spikes in temperature adding ice in sealed containers (eg. a softdrink bottle) seems an option. The following is the most technical bit which could be useful for those who wish to plan to use fans and want to know how big and show fast. ------------- Technical Bit ----------------- You can calculate the rate of evaporation from a tank of water through the following equations: m1 = A.(Xs-X).(25+19.V) where: m1 = water evaporated (kg) A = area of the tank surface (m2) Xs = saturated air humidity (kg/kg) X = actual air humidity (kg/kg) V = velocity of air (m/s) And that can give you the temperature change in the water through: dT = (H.m1)/(c.m2) where: H = evaporation heat of water (2500 kJ/kg) m1 = water evaporated (kg) from above c = specific heat of water (4.186 kJ/kg/degC) m2 = total mass of the water in the tank (kg) So assuming: - A 100L tank 30 cm wide x 85 cm long x 40 cm high. Then the area (A) = 0.3 x 0.85 = 0.255m2 and the mass (m2) is 100kg; - The tank water is 30 degC, giving Xs = 0.0271 kg/kg; - The room temperature of 30 degC and humidity of about 70%RH, giving X = 0.0189 kg/kg; - A fan pushing air over the surface at 2m/s (not especially fast, it sounds like it could be as high as 6m/s for high velocity domestic fans); You get: m1 = 0.255 x (0.0271 - 0.0189) x (25 + 19 x 2) = 0.132 Kg/Hr dT = (2500 x 0.132) / (4.186 x 100) = 0.79 degC/Hr So it seems reasonable to expect cooling of about 1 degree per hour in a smallish tank.

Does this qualify as "Technical" yet?

As a quick and dirty estimate on using ice: If you use a 1.25L bottle from the freezer at -4 degC and drop it into a 100L tank, the simple estimate (dT of 1.25L = 34 degC * 1.25L/100L) gives about 0.4 degC of cooling.

Jacko, Although your theory is correct (disturbing the surface of water makes it evaporate more quickly) I think the dominant effect here is the removal of the humid air from above the tank. So in muggy tropical Qld the effect of a fan will be less than in dry Wellington at the height of summer where the humidity is low and the temperature is in the mid 30's for weeks.* You can calculate the rate of evaporation from a tank of water through the following equations: m1 = A.(Xs-X).(25+19.V) where: m1 = water evaporated (kg) A = area of the tank surface (m2) Xs = saturated air humidity (kg/kg) X = actual air humidity (kg/kg) V = velocity of air (m/s) And that can give you the temperature change in the water through: dT = (H.m1)/(c.m2) where: H = evaporation heat of water (2500 kJ/kg) m1 = water evaporated (kg) from above c = specific heat of water (4.186 kJ/kg/degC) m2 = total mass of the water in the tank (kg) So assuming: - A 100L tank 30 cm wide x 85 cm long x 40 cm high. Then the area (A) = 0.3 x 0.85 = 0.255m2 and the mass (m2) is 100kg; - The tank water is 30 degC, giving Xs = 0.0271 kg/kg; - The room temperature of 30 degC and humidity of about 70%RH, giving X = 0.0189 kg/kg; - A fan pushing air over the surface at 2m/s (not especially fast, it sounds like it could be as high as 6m/s for high velocity domestic fans); You get: m1 = 0.255 x (0.0271 - 0.0189) x (25 + 19 x 2) = 0.132 Kg/Hr dT = (2500 x 0.132) / (4.186 x 100) = 0.79 degC/Hr So it seems reasonable to expect cooling of about 1 degree per hour in a smallish tank. * For anyone who's never lived in Wellington, this happens .......Oooh look a flying sow!

Maybe the wood brought the algae in, or perhaps it's always there, but normally has nowhere to grow? Perhaps there is something in the wood that feeds that algae (such as minerals). If the wood was driftwood, you've got to assume that the 'whatever' can survive salt water. Perhaps a basic solution like sodium hydroxide (caustic soda) would remove it, or at least remove it from the surface of the wood.

Sorry, a slip on my part. These are tungsten halogen bulbs. What makes them special is their high "whiteness" (3500K) compared to ordinary tungsten halogen. I assume that they run them hot to get the extra whiteness (compared to 2200 to 3200K for ordinary tungsten halogen). You could probably pump them even whiter with higher voltage, but life is bound to suffer. One good thing about tungsten halogen is the broad spectrum emission. They have a blue filter to remove the UV they generate. Most importantly, they're small and cheap, cheap, cheap (~$2) and come in a range from 5 to 50W. I've also tried compact 12V CCFL, which does give better light (5000K) but do not live up to their supposed "long life" and are not so cheap (~$20 each). They claim 17K hrs (5 years in my use cycle), but I replaced two sets after they died in only a month (took them back and exchanged them) and the most recent ones only lasted 6 months before they dimmed a lot and I just binned them.

I've plugged this idea a few times. 12V metal halide. It costs almost nothing (<$20) and is only 12V so safe to wire up over a tank yourself. See this post for more detail http://www.fnzas.org.nz/fishroom/non-fl ... html#67537

Oh yeah, Fishy_T's rock mound is really quite something. My girlfriend keeps meaning to get around to siliconing stack of smooth large stones (Makara beach) into an artistic thingamy, maybe I should show her this instead.

Although pumice is nominally granitic in composition, it could contain all sorts of stuff. However, you'd have to assume that if it's been floating around Lake Taupo for the last few centuries it'll be reasonably clean, but it may have just fallen in after sitting in the edge of a bank since 181 AD.

Does it matter what kind of sand you use in a freshwater aquarium? - I was looking at quartz sand for its lovely whiteness, but was told to stay away from it due to dissolved salts. But quartz is just SiO2 (glass), so why would that be important? - What about the equally funky black iron sand?

Although it's not freshwater, get a mask and snorkel and go snorkling! I was just at Balmorel beach on Saturday (northen end in the rocks) floating along in a cloud of thousands of inch-long fish that looked a bit like a species of Tetra. They kept peering into my mask from about an inch away. There were green and purple parrot fish, bright yellow trumpeter(?) plus lots more. Very relaxing. The water's nippy, but I was in for 20 mins without permanent damage.

Has anybody looked at combustion-type CO2 generators? They use these in the greenhouse-flower business. It's basically a propane gas burner. I assume that it has high combustion efficiency to prevent formation of carbon monoxide (CO) which is toxic. Once purchased it should last forever on a tank of propane. They're not cheap, but perhaps a small version could be made for home use with aquaria? I was also wondering if you could use it with the reticulated natural gas supply in your house. That contains mainly methane (CH4), and some trace nitrogen and sulphur. I assume that <0.1% NO2 and <0.001% SO2 in the CO2 wouldn't be too bad for the fish?

Strange. Hysteresis is a bad thing in control systems. Do you have a setting (ie. can be twiddled with) for hysteresis? I would interpret an hysteresis of 1 degree as meaning it will overshoot by 1 degree. that may be ok for use in a fish tank, but it's not a very well designed heater given that you have the thermal mass of the tank to damp out any feedback loops. Digital in, digital out: "going digital" is going to be the downfall of Western civilisation. A heater is analogue (at least to any useful degree unless you happen to be a quantum physicist). All "digital" means is that they are too cheap to put a decent control system on it.

Well, I'm a scientist, I'm a kiwi, I DIY and I have built a tank (which is still intact!) I don't think it matters whether it's neutral, basic or acid cure. What counts is what else is in it. Acetic acid (no acteone) curing silicone is generally recommended for glass, neutral is used where acid cure can cause damage. Clearly you can use neutral cure, because people are doing it. Acetic acid is no more dangerous than vinegar and evaporates away very fast. It's probably not a good idea to put large amounts of acteic-acid curing silicone into a tank with fish in it. But small repairs should be ok. Lot's of silicones contain fungacides. These can kill fish. That's why you look for the "suitable for aquariums" words. I use the really cheap Chinese stuff in caulking tubes. It costs about $5 (compared to Selleys at three times the price) and you could make a dozen tanks if you really felt like it. Selleys is a rip-off. I'm pretty sure they just re-label the Chinese stuff, the tubes can have an amazing resemblance! Bob

I built my own tank (from zero knowldge) and siliconed the walls on top of the base. My logic was that it takes more force to shear (sidways) than to stretch (outwards). I don't like those black strips cheap tanks have down their edges, so mine is just silicone. But I got a bit nervous about the weight of water and lack of my experience, so I put metal corner reinforcing on the outside of the bottom corners to strengthen agains 'creep' over time. My tank is free-standing, so there is no base to provide resistance against creep. It may be easier to rest the glass walls on the worktop, but I thought that if you did it that way you'll glue the base to the workbench! I put all 4 walls in place with a matchstick under/between at each end as a spacer and used masking tape to hold the walls in place. I then just siliconed into the space (slowly and with excess squeezed towards the inside of the tank to ensure no air bubbles in the silicone). Once it was dry I removed the match sticks and then siliconed those spaces. The excess on the inside was cut away with a razor blade.

Ryan, I think this is more of a physics/chemistry problem than electronics. The control system would be easy enough to knock-up, but you'd have had to spend a small fortune on off the shelf sensors. I was considering a cheap & dirty UV/Vis/IR spectrometer based on LEDs and CMOS detectors (possibly with a prism/grating). I'm not so sure about the required sensitivity. Solid state opto-electronics have advanced so much and got so cheap that I'm sure there must be a simple way of doing this. Bob

This is an interesting problem. I was considering how to automate all the monitoring of the tank, but when I saw how much the sensors cost got sticker shock. Most of these sensors are designed to be very selective. It may be possible to get away with much less selectivity in an aquarium if the parameters don't vary much. ie. you know that only a certain number of chemicals can be present and can probably then take this into account. Can anyone give a list of all the ions and molecular species that would need to be monitored in a freshwater tank? - Nitrate ([NO3]+) - Nitrite ([NO2]-) - Dissolved oxygen (O2) - pH (H+) - Amonnium ([NH4]+) - etc?

I have a distinct lack of space, that's whay I use these small bulbs. Mine are also all 12V. I got a bit nervous about DIY with 240V. The 12V CCFL are about A$15, the ultra white halides are $A2. The whole lot cost me about $30 including tranformer, wiring, mounts. If you've got the space, then the new, bigger, CCFL like Whetu's using are probably better if you can get the right colour. Bob

Shinto, Thermal conductivities: http://www.engineeringtoolbox.com/therm ... d_429.html Aluminium 250 W m-1 K-1 (Watts per metre per degree Kelvin) Steel 50 Stainless steel 16 Pyrex 1.1 Plastic 0.1 to 1 Polypropylene 0.5 Wood 0.15 Air 0.024 Why not use something with poor thermal conductivity but easy to work with like plastic and overcome the thermal conductivity with an increase in the contact area. Glass is only twice as good as PP, so double the contact area (more windings) will do the same job. PP tubing tends to be thicker than glass, so you may have to more than double, but PP is very easy to work with, glass is a bitch! Chemists only use Pyrex because it can take the high temperatures and caustic environment. If you can drill holes in floors, why not get really tricky and tap a heat exchanger into/onto/around the water main! That way you don't waste any water. You use a closed-loop heat exchanger from your tank to the main and the main is always cool. The temperature differential is small, but the thermal mass of the main is huge. So instead of wasting lots of water, you just pump your closed-loop exchanger as fast as you can. Also, insted of using water in the heat exchange loop you could use oils, or refridgerants. There were a few comments about water not being a wasteable natural resource. That's not true. Yes, you can always get more fresh water (by distilling the sea, for example). But the amount of 'naturally available water' is often limited. I live in Sydney and haven't washed my car in four years due to water shortages. Bob

Chimera, I run 12V ultra white tungsten halide bulbs (no reflector) (3500K) and CCFL (5000K) in my small freshwater tropical tank (450lx350wx450d). I have been experimenting and found that 40W (2x20W) of ultra white tungsten halides isn't enough to support Val, but Swords do ok. With 60W (3x20W) everyting does ok, but only the sword thrives. I'm trying some new compact CCFL (cold cathode fluorescent) and they make a difference (1x5W = 25W of incandescent light). They're supposed to last forever, but I had 2 fail on me in a two-week period. I took them back and the most recent one has been doing well. I think I'll upgrade to 2x5W (= 50W) and keep 1x20W tungsten for the spotlight effect. Both of these are very compact (I have only 50mm clearance under the hood) and very DIY friendly. However, do not buy an 'electronic' 240/12V transformer for CCFL, it doesn't work. link link Bob

There are also de-worming products available from pet stores. The one I saw initially was a bird de-wormer. I had some guppies infected with Camellanus. Not pretty. Most people say you can't cure it and the bird wormer did not do the job. Levasole (levamisole hydrochloride) is used on Cows & sheep and works (mostly). Camellanus is bad because even if you kill the worm, it doesn't necessairly let go and causes infection.

240/12V transformers can be bought from any hardware store for about $10. They're in the lighting section for the metal halide lamps. I learned an important lesson. Do not buy "electronic" transformers, go for the ol' lump-a-lead brick style. Although the "electronic" ones are much smaller and lighter and look high tech (plus they cost a few bucks more) they are actually an abortion! When you look at the wave-form they achieve a 12V DC signal by 'chopping' the 50Hz, 240V waveform. Basically they turn themselves on and off fast enough to fool a simple 12V DC system into thinking it's getting DC instead of a whole lot of really short pulses. That's ok for metal halides (which are dumb) but don't use them for anything else that has electronics inside, they don't work. You may notice written in small font somewhere that they are for "filament" lamps. The worst thing about them is they put out radio noise! My cordless phone went bananas whenever I went near my tank.