Backyard Aquaponics
A place to discuss aquaponics

I am curious about the maximum density allowed for goldfish per cubic meter or cubic foot (whatever is easier for you guys).

I am looking at about 30-31 kg of fish (66-70 lbs) required to grow my plants and I have 2 fish tanks each of 1000 L (264 gallons).

Can I grow this much goldfish in just these 2 fish tanks? And of course, thinking that mechanical and biological filters are good and running good, great water quality and so on.

I think you will be fine. I keep about 20 - 25 kilos of fish in a 1000l tank. You need good filtration, water circulation, aeration, etc. as mentioned.