Backyard Aquaponics
A place to discuss aquaponics

try again...

Ahh... so ya gunna "laserlite" the shed walls then

And the roof.
Hopefully if I can control draughts under the sliding door, I can make it into a reasonable greenhouse.

Don't forget you don't want it AIR tight... Other wise the humidity would unbearable. The warm air will rise to the top of the greenhouse so any cool fresh are will stay low enough not to cause issues.

Agreed, but being in Can-freezing-berra, cold air spilling under the door could be an issue - as would birds/dogs/rabbits, would you believe a local dog stole a bottle of talc I was using to mark the holes!

Maybe it was cold and having trouble slipping its socks on...

I've put in two large poly tanks both using crusher dust with a bit of dry cement powder added in, and then compacted. I think they call this "cheap mans concrete"? Anyway, full details at the following link:

Water tank installation and site preparation

Towards the bottom there's a BURYING POLY RAINWATER TANKS section that might be useful. Can't see much difference if its corrugated iron except that it might stay in better

Uncle, I am no engineer. I think perhaps context is the answer here. Your concrete tank is outdoors dug into a sloping hill. There is every chance that there would be water looking to drain thru that spot following rain and blue metal will help with that being very porous.
I forgot u were digging the tanks in. I would be looking for solid walls and base, eliminates one failure point.

But failure points are the milestones of my life!

Hope your planning on growing cold tolerant fish ? or perhaps fish-fingers?.
Burying the tank makes heating it almost impossible.

Insulating the perimeter wall is an easy fix

If the tank is buried,,,insulating the walls isn't going to help much as the water will be continually trying to heat the hundreds of kilo's of dirt beneath or just flowing out the top ,if no lid.
I've been going round in circles on whether to have my tank half buried or not and conclude not buried is better.But as with all things , I could be very wrong , so I'll set up 2 X 20 litre buckets ,insulated and covered , one buried other not , both with 200 watt fish aquarium heaters and see the result.

Hi Chappo
The vast majority of the heat will be lost from the top of the tank..freezing air versus nice warm water
Heat moves through soil quite slowly and mainly by conduction so it needs a temperature differential to drive the process.

Sideways heat movement to the cold surrounding soil is reduced/prevented by the perimeter insulation a couple of inches thick.

Any heat that ventures downwards will meet up with increasing soil temperatures, reducing the differential that drives the flow

Edit: A quick comparison of "buried" to "not-buried" tanks in winter (without insulation)
The not-buried sides will be in contact with freezing air but the buried tanks sides are in contact with soil at 50F.
Buried might level out at 50F and "not buried" might become an ice cube

Uncle Yarra I also live near Canberra and we have clearly had the same thoughts re the winter temps. Check my thread for how my system is set up.
http://backyardaquaponics.com/forum/vie ... highlight=
After running for about 6 or 7 months I can report that the water temps in the buried fish tank are much moderated compared to the room/shed temps.
I measure temps all the time and over the last 3 weeks the room temps have varied from a low of 7 degrees up to a high of 30. Tank temps in the same time have been between 13 and 22 degrees. And room temps vary by as much as 17 degrees over 24 hours while tank variation over the same 24 hours was less than 3 degrees.
Clearly the large volume of water will have a major heat storage effect but I am sure that the buried tank makes that temperature stability even more marked.

Thanks JimA,
If it stabilises temps in frosty Burra then it'll be just the trick for Sutton.
BTW, the bricks around the bottom of the shed - is that a greenhouse/thermal barrier thing?