Heating options for fish tanks

[daniel]

I have been fiddling around with different methods of heating my 2300 ltr tank trying to find a low cost way of heating.

Firstly I made up a coil of copper pipe and fitted it into a 25 ltr drum filled with water.
Set up a gas burner under that. It worked fine, raised the water temp by 4 deg in a 12 hour period. The down side is that it burnt $20.00 worth of LPG.

I made up a grid of sorts out of 1” black poly pipe and put it up on the shed roof. I managed to raise the temp from 15 deg to 18 deg over the day (3 deg C), but at night the temp dropped back to 15 again.
Last winter I only had a 600 ltr tank so it was easy to cover every night. Making a lid for the big tank is what I will have to do, that is obvious.
I think if I go and get a 100 mtr coil of 3.4” thin walled low pressure irrigation hose and run the water through that up on the shed roof, it should improve. More distance for the water to travel and therefore heat up.

The good part about living in S.E.Qld is that our winters usually have nice sunny warm days around 22 to 25 deg, the bad part is that it hardly ever rains !!!
So the solar hose thing together with a lid on the tank should do the job.

Muzza

I am all for sustainable water heating. Water takes sooo much energy to heat that it can ends up getting prohibitively expensive for projects like this, AND will produce large amounts of CO2.

Living in Australia allows us the luxury of sunny weather a lot of the time, so I am a keen fan of solar heating of water.

Here are a few projects i have noted from around the net that could be adapted to heating of water.
http://hacknmod.com/displayMOD.php?hack=309
http://www.thesietch.org/projects/solarthermalpanel2/index.htm

The size of any medium to large size setup should, i believe, be looked at in the same manner as swimming pools when it comes to heating. There is a range of solar pool heating methods around. That in mind, most roofs, if orientated correctly, would make perfect mounting surfaces for a solar water heating setup.

Sorry if this sounds like a rant

[Murray]

Daniel, that is not a rant.....I am with you all the way.
Thanks for the links....later tonight I will go in and have a good read.
Murray

[njh]

I've just published an article in the latest renew (100) about how to heat an aquaponics tank using solar power - I've getting more than 5kW and 75% of heat from $100 in parts. Would easily scale to very large systems.

Those designs posted by daniel look a bit fiddly for the amount they will collect. I would look at trickling water down a piece of old, unpainted corrugated gal roofing iron first. Rust is good. Cover with thin polyethylene film, then polycarbonate roofing to form a double glazing with the ideal plastic for each job. I got about 20% conversion efficiency from this some years back, and it's very simple to make. You can put it on top of an existing roof.

[Jonty]

njh,
You hit the nail on the head with the mention of double glazing. I used a solar heater to melt beeswax years ago and it was really efficient with double glazing.

[njh]

njh,
You hit the nail on the head with the mention of double glazing. I used a solar heater to melt beeswax years ago and it was really efficient with double glazing.

Yeah, that little bit air really makes a difference. I melted polystyrene foam using a single layer of polycarbonate and some shadecloth. That's over 100C!

[GaryD]

Hi njh,

I like your solar water heater idea. It's much simpler to put together than all of the other suggestions that I've seen previously.

Since you wouldn't need it during the night (in fact, it would have the reverse effect), would you suggest having the pump on a timer?

Gary

[Frank]

Gary. I've been trying to find the link to the article so I can have a look.

Where did you find it?

Frank

[njh]

Hi njh,

I like your solar water heater idea. It's much simpler to put together than all of the other suggestions that I've seen previously.

Since you wouldn't need it during the night (in fact, it would have the reverse effect), would you suggest having the pump on a timer?

Gary

Actually, what you want is a differential thermostat. These are easy to make if you do electronics (I use 1-wire bus for my temperature measurement - cheap and easily extensible). You turn the pump on only when the temperature difference between the gal metal and the tank is suitably far in the right direction.

A timer would be a cheap starting point (but would require changing as the day length changes). Remember that it won't heat up instantly, especially from a cold night - give it a few hours of daylight to warm up first.

You might be able to salvage something using a 'pair of thermocouples' salvaged from a central heating unit (not sure of the volts / temperature difference). These are designed to switch on when the temperature difference is high enough. However, the difference may not be high enough, they probably will need a diode added (use a schottky hot carrier diode for minimum drop) to make them work in just one temperature direction and they won't have much length (perhaps 50cm from hot to cold).

I can think of all sorts of simple analog circuits to try using basic thermisters, but to be honest, I bought a USB to 1-wire transceiver for $80AU and I can buy as many thermometer chips as I like for $4 each. Then you just need a way to turn on a relay using a computer and you're done. (There are a billion such circuits on the web using the parallel port)

If people are interested in building a computer to monitor their greenhouse, I've found a good low power embedded computer that comes with linux preloaded and all the ports you need to talk to 1-wire, turn on and off relays, connect to my water level sensor(http://njhurst.com/electronics/watersensor/) and log all the data on the web(http://njhurst.com/GHT.svg). I'm happy to help people set one up.

[Macca]

I've just published an article in the latest renew (100) about how to heat an aquaponics tank using solar power - I've getting more than 5kW and 75% of heat from $100 in parts. Would easily scale to very large systems.


I've not heard of that publication. Is it available on the net? How would we best get a look at the full text of your article - sounds interesting.

[njh]

I've not heard of that publication. Is it available on the net? How would we best get a look at the full text of your article - sounds interesting.

The best way would be to buy the magazine:
http://www.ata.org.au/publications?page_id=15

I hear that being their 100th's edition, it's going to be a bumper-crop too.

They are not-for-profit and can only produce their magazine if people buy it. (I was not paid for writing my article, but support their cause)

Gary was talking about my trickle collector suggestion. It's not the same, but it's easy to make. I made my prototype in an afternoon. The trickle collector is well suited to putting over an existing garage, carport or shed roof. It is not as efficient, cheap or flexible in use as the system in renew. You might try the idea out using an existing piece of corrugated iron and some plastic film first to see whether it is practical for you or not. Jonty is absolutely right in pointing out the advantage of the double glazing: if you use a single layer glazing you will get condensation on the glazing which will transfer a lot of your heat away. Per square meter this is still a very attractive approach, and much cheaper than the swimming pool heating stuff (I was quoted about $100/m^2 for the swimming pool stuff, this is more like $30/m^2 new and free corry iron is very easy to get, the system in renew could cost as little as $2/m^2 new).

(Admin: Perhaps this discussion should move out of Murray's system?)

[Frank]

njh, sounds great.

Perhaps some diagrams might assist people who might not be able to visualise what you're saying.

[njh]

njh, sounds great.

Perhaps some diagrams might assist people who might not be able to visualise what you're saying.

No diagrams, but here are some photos of prototype 1:
http://njhurst.com/solar/20060215/

That used new colourbond (our new garage roof), but I tried again with the old stuff; can't find the photos. There are a bunch of optimisations you can make. Perhaps you could write an article about it and publish in renew?

There are several competing optimisations - pump energy, solar collection efficiency, heat loss, flow rate. If I did it now I would use a variable speed pump and run the pump just fast enough to balance heat removal with heat loss.

For fish water heating you also need to be careful not to boil your fish if they get too close to the outlet.

[GaryD]

Hi njh,

I like your solar heater idea much better than the swimming pool heater arrangement.......it costs less and it's technically more elegant.

A few thoughts......

All small bore tubing quickly clogs with the bio-film that builds up in AP systems.....and small holes in tubing clog even faster. I'd suggest a simple weir arrangement so that the water overflows from the top of the collector and can never become blocked.

Another roofing iron profile (like V-crimp) would offer greater heating surface.....for the flowing water to make contact....than the corrugated
sheet you've used.

A small temperature controller (usually used to switch ventilation fans in greenhouses or grow rooms - available from most hydroponic shops) could be used to switch a small pump on an off to enable the water temperature to be maintained within predetermined limits. While this would add to the cost, it would avoid boiling the fish.


Gary

[Macca]

Your suggestions are all good ones Gary - but in relation to the pump one I think NJH is talking about the stream of water comign into the tank after going throught the heating system. Of course this issue could be avoided by having the inflow coming into a netpot or something so that water can disperse a bit before it gets to an area that the fish can get at.

[Macca]

NJH - when do you think the edition will be out (renew 100).

[njh]

Hi njh,

I like your solar heater idea much better than the swimming pool heater arrangement.......it costs less and it's technically more elegant.

A few thoughts......

All small bore tubing quickly clogs with the bio-film that builds up in AP systems.....and small holes in tubing clog even faster. I'd suggest a simple weir arrangement so that the water overflows from the top of the collector and can never become blocked.

Yes, I found that it was a problem, I considered a channel with v-cuts all the way along. The other option is to simply pump the pressure up once a day. Also, letting it dry and and cook each day is probably quite effective.



Another roofing iron profile (like V-crimp) would offer greater heating surface.....for the flowing water to make contact....than the corrugated
sheet you've used.

Harder to obtain - the stuff I used was already on site. But certainly there are better choices. If I were trying to make hot water I would probably use corrugated, black annodised aluminium with smaller channels, and glass glazing.


A small temperature controller (usually used to switch ventilation fans in greenhouses or grow rooms - available from most hydroponic shops) could be used to switch a small pump on an off to enable the water temperature to be maintained within predetermined limits. While this would add to the cost, it would avoid boiling the fish.

Actually, that's a good point - although a differential thermostat is more efficient, simply turning the pump on when the collector temperature exceeds 40C would probably be sufficient. I was more concerned with an incoming stream of hot water - you won't be able to heat the tank up sufficiently to boil it, I think, as evaporation increases rapidly above about 30C. (that statement is not correct, but near enough for this discussion)


Your suggestions are all good ones Gary - but in relation to the pump one I think NJH is talking about the stream of water comign into the tank after going throught the heating system. Of course this issue could be avoided by having the inflow coming into a netpot or something so that water can disperse a bit before it gets to an area that the fish can get at.

Yeah, exactly, some kind of mixing process is what I'm thinking of.


NJH - when do you think the edition will be out (renew 100).

It's the July issue, so I'd guess in the next couple of weeks.

[Macca]

Thanks for that.

[Frank]

Yeah thanks njh. Had Pm'd you to figure out what was going on, couldn't find it anywhere

[GaryD]

Hi,


.....it would avoid boiling the fish.
Sorry, this was my bizarre sense of humour at work. I agree that it's unlikely that the water in the tank would get that hot.

Actually, that's a good point - although a differential thermostat is more efficient, simply turning the pump on when the collector temperature exceeds 40C would probably be sufficient.
Since we're only trying to move the water temperature through about 5 - 15 degreesC.....in my case from the current 14oC to about 22oC......it's more likely that we'd have to turn the pump on when the water temperature dropped below the optimum......and then off again when we reached the top of the range.

The risk of burning the fish would be minimised by ensuring a good flow through the collector and by discharging the return flow underneath the surface of the water.

Gary

[Murray]

NJH,
I notice you have used clear poly carbon or the like over the corrigated iron. Would black builders plastic work as well or does it need to be clear or semi clear to allow the suns rays to get to the iron at the back ? Sorry if that is a silly question. It is just that I have some of that black plastic. Come to think of it I have some semi clear greenhouse plastic....As soon as the sun comes up I will be into a frenzy of experimentation.
The problem I have had so far is being able to process enough water during the optimum daylight hours between about 9:30 and 3:30 approx.

The 50 mtr roll of 19mm black poly pipe I have up on the roof raises the temp of the water coming back to the tank by about 1 deg, and to achieve that it has to be running very slowly and it just does not make enough difference in the fish tank. I guess it is a big ask to heat 2000 ltrs by 4 or 5 deg in a day.
Muzza

[Macca]

NJH - how many square meters of the iron type heater you have made would you need to heat the 2000l by 4 or 5 degrees do you reckon?

[Quietly]

Hi Macca,
I might jump in on this discussion.
Given that a Solar Hot Water System usually works on a panel size of 2m x 1m = 2 sqM. A 600L system is often sold with 3 panels, 400L with 2 and 200L with 1 - roughly anyway.
The temperature increases in these systems are very high compared to what we in AP will need but given ball park figures of say 1 sqM heating 100L say 30 degC in 1 day a 2000L AP system would need say 3.33sqM.
1sqM = 100L = 30degC in 1 day
1sqM = 600L = 5degC in 1 day
3.33sqM = 2000L = 5degC in 1 day or 1sqM = 2000L = 5degC in 3.33 days
That rough mathematics works for me but all are welcome to dissect this further.
Given the home made heaters we will make may not be as efficient as the you beaut bought ones I still believe a well built heater attached to a 2000L system will give an acceptable temperature rise over 5 days.

[Murray]

Hi Quietly,
Thanks for those estimates. I am going to give it a go. I have some sheets of corrigated iron 4.8 mtrs long x about 700mm wide. I think I will use two sheets. NJH, Painting the sheets of iron with matt black paint ought to make make a big difference ? What do you think ?
Muzza.

[Macca]

That's weird - I'm sure I posted to this topic earlier what I am about to say again. In fact I am certain because I looked at the post after I made it and noticed how many spelling errors I hade made. Seems to have been deleted.

What I said was:

I have had solar hot water heaters in the past. I can remember from looking at them that they have a black material under the glass, but I am not sure where the water flows, presumably under the black stuff. I wonder what the black material is. It would have to be food grade at high temperatures. I was wonderring whwther it is black annodised aluminium - which is what NJH was saying could be a good material if you had your choice.

Dunno about using paint - wouldn't that end up in with the fish?

[GaryD]

Hi Macca,

If it was part of the material that was in Murray's System thread then it's likely that it was deleted.....accidentally......while I was trying to merge two threads.

The other possibility is that your log-in timed out before the post made it through to the Forum. We've extended the log-in times to avoid this happening. I've got part way through a number of posts only to lose them when I've attempted to submit the reply.....due to log-in time outs.

Only offensive or obnoxious posts will be deliberately deleted from this forum. We may periodically prune forum threads of non-essential comments........just so that members can access the information on the forum in a timely manner.

GaryD