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.
Personally, I dont start all of my fish at the same time. Right now i have 4 fish tanks all running in one system. I am mindful to keep fish of the same size in each tank but i can stagger production and harvest times.
There's no need to worry about reproduction in a 300 gallon tank. unless you "rescue" the eggs or the fry they will not be able to escape predation. .
Rainman,
I read a lot of badflash's information and other sources I dont remember what tilapia information i have taken from his threads but the mention was only for credit the egg tumbler idea because that is where i got the idea to build mine. Any information in the thread is based on information from multiple sources cross referenced with my limited but very successful experience with raising tilapia.
I agree, that if the mother is allowed to brood the fry to full term, I typically gain more fry. However, this means moving all of the other fish out of the breeding tank because fry do not live very long in a 55 gallon tank with a full grown male and 4 females. I think getting less eggs early has most to do with the mother swallowing eggs in her panic while being handled. Of the eggs that make it to the tumbler, I have good hatch rates... Above 90%. Personally, i only try to save a couple dozen fry each year so if i get part of one brood i am set.
Yesterday, 6/11/2013, I was moving a couple of tilapia from my main tank to the HSB tank for algae control and accidentally caught a brooding mother in my net. I wasnt expecting the brood so i had the wrong net and no nursery tank prepared. Still I was able to collect about 50 "sac" fry and my tilapia breeding for this year is now complete!
A follow up note. The eggs also seem to be stronger than the swimming fry. I have killed a few hundred fry because the mom was spitting the fry out in the net and then crushed them with her flopping around. The eggs dont seem to crush as easily.
I owe you guys pictures of my "current" system. These are pictures from october 2012 of the START of a very big system but I have decided to go a different route. Once i get my first ferrocement tank and grow beds built these IBC's will be relocated to the garage for breeding tanks/wintering system. I think ibc's are an eyesore and i think i can make the system much more aesthetically pleasing with ferrocement.
IBC's on cinder blocks, I am sure there is a white trash joke in here somewhere. The three "higher" ibc's overflow into the grow beds which drain to the two lower ibc's
Wood grow beds with pond liner. It's tough to see but the 2 IBC;'s on the ground are connected via 2" pvc. I am only using one pump.
Expanded shale media, A 4" media guard around the bell siphon that i have not yet gotten to work exactly right. I am just using a stem pipe and the grow beds are constantly flooded.
I'll try to take some current pictures later today and show some of the plant growth. Or a video may work better?
brian
