Backyard Aquaponics
A place to discuss aquaponics

Not actually bricks- a concrete perimeter I poured after the shed constructors left ALL the wall cladding at least 200mm above the level of the floor!
I can only assume that they expected me to pour a really thick slab- which I had no intention of doing.

Hex , thanks for the thermal heat transfer in dirt explanation,that was the missing link in my thinking. Things would change if the soil was open to rainfall , but the area is covered.
I'm lucky as I live quite close to the ocean in Sydney ,so have quite stable soil temperatures , in fact i'll probably only need heating a couple of months a year.

Test reults are in ,, do NOT bury your tank if you wish to keep it warm. Conversly ,, if you want to keep your fish cool/cold ,, do bury.

Hex ,, sorry my friend but every bone in my body suggested burying was wrong, but I kept reading about people doing it. Test prooved it and real world examples show it. Only under-ground housing I know of in Aus , is out in the Opal mining areas ,, and they do that to keep cool.

Tank insulation test's next ,,think I have a winner here before starting ..... new extension on my house I have used it under the colour-bond roof and its AMAZING !!! Pre insulation room was unbearable ,, now it's cool even on hot days,,, I laughed when the insulation guy said it had an R4.5 rating , but it is truly amazing stuff.

Care to share your test results Chappo... I'm intrigued...

How did you go about testing and what were the results

Ok , first to set test parameters. Sydney site , 2 drums of 200 litres , one buried ,, well 90% buried , other above ground on a pallet type arrangement and insulated.
Note ,, underground drum given top of container insulation, airial container insulated on all sides. 200 watt aquarium type heater added to both drums , initial temperature of water , about 19 C , both thermostats on heaters set at 23-24 C ( the temp I wish to achieve as a minimum constant for Jade Perch). Pissed off to work , night shift is so NOT fun , returned in morning found ,, airial container was at thermostat temp ( 23-24) , may have been that way for hours and thermostat switching on and off ( but that is an assumption) , below ground tank approx 19 -20 C, so I assume had used 200 watts power all night but achieve very little because of heat loss to surrounds.
Conclusion , burying tanks is a FANTASTIC way to keep temperatures resonably constant ,, the problem comes when that constant is below the desired temp.I.e , if i lived in Cairns ,, ,, yep i'd bury my tanks. Air is far more easily insulated against than earth. Think about going out on an Autumn day at say 16c air temperature ,, I find that very comfortable ,, now think about taking a swim in 16 C water ..... it's blinking well cold,,, why ..... simple , water and almost equally , dirt , have a much greater capacity to remove heat. Another example ,, say we heat a common butter knife to 200 Celsiuys ,, then drop it in water ..... or push it into soil or hold it in the air ..... I think we all know which one would be hottest after a few seconds.

Chappo I actually agree with you about insulating the bottoms of tanks as well as the sides. Reasoning for me is that our basement is unheated. My office is downstairs and in the colder months I would sit at the computer with my feet on the concrete slab, and over the course of hours it would pull so much heat out of my body that I would have to take a break and go upstairs. My feet would ache because they'd lose all their heat. It would be like camping without a sleeping pad under the sleeping bag - the ground will suck all the heat out of you if you let it by not having a thermal barrier of some sort. Things might start to equalize starting around 60 degrees or less but by then the tilapia would be dead.

This all assumes the fish need to be above 50 degrees, otherwise no insulation just dirt for me.

I guess it depends on the situation to some degree and an extended time scale of the test.

Dave`s basement isnt going to get the same amount of solar gain that would be available in the open so its sumping what heat is available like a sponge. If he had free heating and left it running flat out for a year or two to charge the mass, it would stay toasty when switched off and only need a small top up to maintain it

In the open with full sun you have at least 1100w per sq m per hour..enough energy to heat 200L of water by 8.5F every hour for free
When you multiply that figure by a few summers, its a vast amount of energy which will make a difference to the temperature at the extremities of the mass which need a one time "charge", but its free anyway. Beyond that one time charging cost.. its all gravy.

In the summer there isn`t much of a temperature difference between the water and air. The same test in the winter would probably swing the other way as the water can`t go much lower than ground constant. The above ground tank will take air temp levels as the baseline which are likely to be lower than 50F so you`d need more energy to make up the difference.

In a nutshell, a heavily insulated above ground tank will lose less heat initially than a perimeter insulated buried one. The former may overheat in summer as there`s nowhere for excess heat to be stored so essentially it`ll go to waste and you may need more heat in winter when the air gets colder
The latter will take longer (maybe years depending on the size of the mass) to reach a new higher temperature balance point but once it gets there it`ll be pretty hard to shift the temperature.

Interesting!

If it were me, I'd bury the tank, surround it with a large 'coil' of poly pipe (not directly around the tank - leave some earth/insulation between it and the tank). Use solar heating and a small pump to circulate hot water through the 'coil' during the day and let the heat in the earth keep the tank at a very constant temperature overnight.

It may take some time to warm enough earth around the tank, but it would get there and the cost of running a small pump would be considerably less then a thumpin' water heater...

Just curious but isn't there a you know what load of variables in this? eg what the 'ground' is made of how wet it is etc.

Yep, a million and one variables.
If you have a high water table you`re doomed

Nah, just top up the water table with hot water and it should be right to go once you've weighed the tank down with a few rocks

Amazing. I post a question and the next thing some guy has two tanks rigged up and is measuring temperatures for me!
Great food for thought and I think I will have to put some kind of heating system in when i replace the gal sheeting on the roof.
I just bought 2 Ebara Optimas on Ebay so I should have plenty of excess flow to divert to it as required [yes, yes, head issues, but the flow requirement should be very small]

Also I guess for evaporation reasons you'd want the water temp to be just below the air temp, yes? Otherwise the warm water will want to all evaporate into the air until it's the humidity is way up or the water's gone?

Well, at least I buried my tanks for the right reason - cooling in summer