Cecil,
You are probably going to get a similar answer from keith because we tend to share the same philosophies.
Warning, aquaponics is addicting. You will start with a 300 gallon system and once it's built you will think of a half dozen things you can do to improve it... expand it... and once you apply your improvements/expansion, rinse repeat.
Like most things "it depends". Rainman pretty much has the consensus down which is kind of the base line i would recommend to anyone for their first go. The one lb of fish per 1 square foot of media (~7.5gallons) rule of thumb is also a little bit subjective because what media are you using? One cubic foot of 3" river rock has a lot less surface area for bacteria than the same volume of pea gravel. Once your system is mature you can start to increase your fish load to see when water quality starts to suffer. (if highest fish load is your goal)
Your link doesnt seem to work because of some weird characters, but I have tinkered with that Wilson Lennard's spreadsheet and it seems to be based off of the UVI research and more accurate than any rule of thumb i know. At a glance there is something wrong with your calculations because fruiting plants take way more nutrients than leafy plants and there's now way you can grow more tomatoes per lb of fish than cabbage. Not without additives anyway. Remember that Aquaponics is nitrate rich (vegetative/green nutrients) and a lot less on the Potassium and Phosphorous department (flowering/fruiting nutrients) which tomatoes will require a lot of.
I dont use additional filtration or settling tanks in my systems so I try to keep a modest fish load. I allow for the solids to break down in my grow beds (with help from red wiggler worms) which adds micro-nutrients to the system through mineralization. The only additive i use is a tablespoon of cheleated iron every few months. Sometimes i bury chicken eggs shells in the grow beds to recycle the calcium but i dont believe i "need" to. I get calcium and magnesium in my tap water.
Brian,
Thanks.
What do you consider a modest fish load? I'll be eventually going up to about .50 lbs. of fish per gallon as I do some serious mechanical filtration along with 4 cubic feed of mb3 media for biofiltration after mechanical filtration in an mbbr filter, which has enough surface area for about 200 lbs. of fish.
Could the tomato calculations seem off due to Glynn's heavy fish load of 0.50 lb.s of fish per gallon of water? Glynn also does not do any water changes and he uses redclaws to clean things up somewhat in the raft tanks. His redclaws actually take residence in the roots of his plants.
