Backyard Aquaponics
A place to discuss aquaponics

Hi,

My new system will have a 4cube tank (pvc liner), sunk into the ground. The fish tank and grow beds are inside a greenhouse. I would like the water to be at least 15 degrees C or more. The average minimum winter temp is 7-8 degrees C, and the average winter daily maximum is about 18degrees C. I'm thinking that I'll need to line hole for the fish tank with polystyrene or card board or newspaper to reduce the amount of heat loss? Is this necessary or am I wasting my time?

Thanks
Rob

Regardless ... IMO.... you'll have to heat your water to maintain the temp you want...

And heating 4000L aint gunna be cheap....

Actually... noticed you say you'll be inside a greenhouse.... you might go close... might...

Thanks Rupert. ok, so yes to the insulation I'll see how it goes this winter with regards to temperature. If it doesn't maintain 15degrees c or more, its not the end of the world.

If you're inside a greenhouse... and had a floor (like concrete or tile) ... that could attract and hold the daylight thermal warmth... then perhaps the ground temp would remain higher... and the insulation may not be needed.. or of benefit...

I'm sure there are others more qualified to comment on this aspect...

Great, thanks. The floor is mostly going to be covered with flood and drain gbs:) Its built outside on sandy floor. There will be an additional 1 cube of water in a DWC bed, so i'm hoping that it will help store a bit of the warmth.

if forced to heat artificially, I would look into introducing an instantaneous gas water heater to the system. As they fire up on water flow, you could regulate the heat to much lower temps by switching a pump with a thermostat.
Heaps cheaper than electric.
The greenhouse will help to contain the heat too.

robc, Before insulating etcetera, dig a small hole to the depth of your tanks and place a thermometer at the bottom and cover over with the soil pressing down as you go. An aquarium type thermometer with bulb and a cord to the read out will help. Next day (to allow things top stabilize) read the temp several times during the day and the should give you a pretty good idea of what's needed.

The earth temps (below the surface fluctuations) are very stable and may help to stabilize the tank temps both summer and winter - same principle as earth bearming or underground houses. An educated guess of your latitude and climate zone is that the ground temps will be fairly stable at approx 17 degrees C at approx 1 metre deep. So a variable to consider is how deep the tanks will be and how much of their sides will be earth sheltered/covered.

Another major variable for tank water temps will be the temp swings in the greenhouse. The grow beds, and the constant water air interaction they induce, will create temp swings that parallel those of the greenhouse - albeit with thermal lag commensurate with the thermal mass of the tank water (and earth coupling).

In some cases insulating the tanks may actually be the wrong thing to do, as you may want the tanks to couple with the thermal mass of the earth and increase temp stability.

Just a thought. mc

Maintaing warm or cool is difficult without a lot of effort i have done heaps of experements [see my system around page 80] i have ibc/s buryed insolated with 3 in cool room cladding one i let run normal through grow beds the other i pumped through 1 1/2 in polly buryed 2 meters down with a water agg pipe there to keep the ground damp after 2 days the 2 mt deep thermometer was the same temp as ambient and both tanks were the same i also have heated a tank and beds with natural gas in a closed invirement in a glass house with some success
i have found air giong in a fish tank will heat or cool it the best way to maintain a high temp is heat your ft and run a biofilter

Thanks Kuda, I'll keep that in mind if I go the heating root!

Thanks McFarm. We dug the hole yesterday, 1.1m deep. The ground didn't seem too cold, but I'll try the thermometer suggestion to gauge the temperature. If it is 17degrees, its a bit of a double edged sword. It'll maintain temp in winter but in summer it'll also keep the water colder, but I guess I'll see how it goes:)

food&fish, thanks a lot, your experience is invaluable! Did the temps stay similar after more than 2 days?

Thanks Rob

Rob i just gave up and went with the flow and get fish to suite silvers all the time and trout in winter

Nice! keep it simple! Well, hopefully the temp in the tank will stay above 15, but if worst comes to worst I'll get different fish

+1
I never bothered due to the respect I have for Milne's research. Too much time, effort and money would need to be expended... I have a hard enough time paying for the mortgage.