Backyard Aquaponics
A place to discuss aquaponics

If you line the frame with fibreboard or similar, you wont need to build it out of solid timber, leave double or trible spaces between the longitudinal beams.

Depending on what diameter your pools are, you could score some steel trampoline frames off Freecycle. I picked up two for free recently, an 8ft and a 12ft.
Rivot some steel banding around the outside of the legs to stop them moving out under the pressure and line the ring with some 1/2" plywood.
I turned down a 16ft trampoline.. too big and too far away, but it would have made a reasonable priced 5000L growbed even with plywood and liner costs

I have a 30 foot long by 3 foot wide grow bed out of wood and liner. It sits directly on the ground so I need not use plywood for it. The biggest trick is you need some really sturdy stakes or posts along the sides to keep the lumber from bowing out along the sides and to keep the whole thing level. This bed has a sump pump in it and other beds cascade into it.

I suppose it might be reasonable to do something like this with concrete block too but I don't have much experience with that or how best to go about it.

Since you won't be digging holes for the fish tanks, you might be better off putting the grow beds lower than the fish tanks and doing CHIFT PIST but you will still need to figure out how to do the sump.

Has anyone used colourbond metal roofing for a growbed. i've just bent a 3.5m sheet up today (into a wide U shape) and before I finish it, I wonder if anyone has any hints for it.

If it's zincalum.... then you could have problems with zinc leeching over time... especially with the acidic nature of AP water...

Must be lined.

OK
So now I'll get some liner.
PS this was too long to bend by hand, it resulted in some minor scrapes.

tomorrow i buy some more fish, so my question is
Which is easier to grow in Brisbane Silver perch or Jade perch?

I think you'll cool off too much through winter for Jades... and Barra.... unless you're prepared to heat...

So Silvers are the go... but may not be ready until after Xmas...

If you think you can keep your water below 20 degrees for the next six months...

Then trout are a possibility... if... you can keep the water temp down...

Is it too late to say, couple of boards and g clamps and at least 2 people to bend it. Or if you buy it at a steel yard just ask to use there bender.

the guy at the fish farm said that silver's would be go for my purposes, so that's what i got.

ph is close to 7.0 (prob 6.9)
ammonia is negligible (tested with kit)
tank in in shed
fish (Silver perch) arrived yesterday arvo, no dead for first 4 hours
then overnight 6 died.
today they are dying about 1-2 per hour.
I thrown half a bottle of cycling bacteria into the water, no effect noticed except for cloudiness
have also added some carbon to the cyclinder (will explain the cyclinder later but is contains entry bottom, exit top, lots of birdnetting and an air stone)
Help what next to do.

ps the chinese water cress is very young.

Are you salting. New fish can get a shock when placed into a new enviroment, ph, temp, o2 change etc.

i threw in 1 kg of plain salt the day before the fish arrived (no mention of iodine on the packet)

When you say "plain salt"... just what do you mean Alex...

It's not just the iodine in table salt that's a concern.... but the anti-caking agents they include...

By preference ... always use pure sea salt... such as Sunray Pool Salt.... $9/25kg bag... Bunnings, IGA etc..