Backyard Aquaponics
A place to discuss aquaponics

I was just wonderin if it would be alright to have between 20 to 30kg's of fish swimming around in aprox 600l of water while my gb's are all full?
Any opinions would be greatly appeciated

600 litres of water ..... if your FT is large that could mean only a 1cm depth,,, if small it could mean 60cm or more.
A little more detail would help answer the question

True, i didn't think of that
My tank is a 1200l IBC, so with bout 600l left there would be aprox 50 to 60cm of water left.

50 - 60cm water depth should be fine for the fish. Having said that , a lot of people work on trying to keep an almost constant height ( depth) in the tanks. Take a read through the thread "sequencial ....., is it the holy grail of aquaponics".

The way I see it, 18 kg is the max fishload you would want.
Double that is asking for mass murder

If my math is correct...
600lts / 30kg = 20ltrs per kg of fish

The max I will be running would be near
4000ltrs/100kg = 40ltrs per kg of fish

and that will be a steady ramp up

Your stocking density is directly related to your filtration capacity.... feed rates and aeration...

Personally I wouldn't hold more than 10-15 fish in a 600L tank.... and that's assuming they're 800gm-1kg full grown....with all the correct filtration, aeration and water turnover parameters... and with constant monitoring

It should only be bout 600l for approx 10-15mins b4 starting to refill.

... yup.... stick a 1kg fish in a 20L bucket... and try and keep it alive...

Even if you can... it'll probably commit suicide from depression...

So this is a minimum volume, like a sump.... 600L....

Regardless... as above...

Also there will be water consumption..
you wouldn't want to leave the top up with a full system of plant growth
With that fish load you would want as Rupe says, maxi GB's and plant takeup.

I'm not usually one for opinions, but - in my opinion, that stocking density is probably too much for 1200 litres, let alone 600 (albeit for 15 minutes). I have 80 odd Trout fingerlings in 1000 litres, with a powerful flush of water for 15 minutes in the hour - and it is still a struggle to keep the water clean.

You would really need to have a constant flow of water through the tank 24/7 to continuously stock that much weight.

My fingerlyings have a constant flow 24/7 to keep there water clean.

And that's not just water turnover... it's water turnover through xxx volume of bio-filtration...

completely left out of my equasion

Hi Jono and Welcome

My system has 80 odd silver perch in one 1000 litre IBC. The fish range from 40 grams to 350 grams. I would guess somewhere around 15 kilos total (probably around 25 kilos by XMAS). 1500 litres of filtration with 24/7 pumping with autosiphons. The water is crystal clear and the IBC is spotlessly clean. I think 600 litres would be pushing it however.