Backyard Aquaponics
A place to discuss aquaponics

I havent considered DWC primarly because of floor space.

Aqauponics aside, just taking into account the aquaculture system your consultant has designed for you... the stocking densities and FT water volumes you are quoting don't match the bio-filter volumes... not even close... at least not for any kind of filter or filtration material I'm aware of.

The best bio-filtration media I'm aware of is K1, which will support a maximum of 250gm of feed per 50L, per day... which equates to about 4lb's of feed per day for each of the 100 gallon filters attached to each of your 930 gallon fish tanks... that's if they are K1 moving bed filters.

At your minimum quoted 5lb per ft³ stocking density, each of your tanks would be holding around 620lb's of fish at maturity... We're not allowed Tilapia here, so I'm not sure of the optimum feed rate for them, but I recall reading in the past of commercial rates of 1.5% - 2.0% biomass/per day (I may be wrong) of good quality, high protein feed... so let's use the lower rate of 1.5%...

At maturity each of your tanks of 620lb's of fish would require 9.3lb's of feed per day... more than double what your filters could handle in a best case scenario. At 2% biomass/per day they would require 12.4lb's per day... over 3 x what your filter can handle.

At your maximum quoted 9lb per ft³ stocking density, each of your tanks would be holding around 1,112lb's of fish at maturity... at 1.5% biomass/per day feed rate... your tank of 1,112lb's of fish would require 16.7lb's of feed per day... over 4 x what your filters could handle in a best case scenario. At 2% biomass/per day they would require 22.2lb's per day... over 5 x what your filters can handle.

...and even with some kind of miracle filter, the water changes required would be massive... and with the stocking densities you're talking your primary and back-up air supplies would want to be mighty impressive.

So, if my numbers are correct, I reckon each of your 930 gallon FT's with 100 gallon K1 filters, could support about half the 5lb's per ft³ you want to achieve as your minimum. Sure you could get more fish per ft³ of water, but IMO you would also need more filtration in ratio.

Then again, maybe I've got the sums wrong... I dunno... and I don't have anything to do with Tilapia.

Now for the R.O.I... How much is Tilapia worth per pound, selling wholesale, in the US?

+1 Mr D

Damage thanks for your input your right the filters I have now were from my old setup outdoors 3lbs/cubic ft the new system will be upgraded accordingly to ...I am sure i can hit 5lbs... 9lbs is the extreme end but still doable I belive with upgraded filtration and enough DO.

"Now for the R.O.I... How much is Tilapia worth per pound, selling wholesale, in the US?"

Are you moving this amount of fish locally or selling to a wholesaler/distributer?

What are you using for oxygenation?

what is your current (3lbs/ft^3) biofilter setup?

cut/paste from here https://www.google.no/url?sa=t&rct=j&q= ... GQ&cad=rja

The general rule of thumb is that highly aerated systems in which fish are fed for good growth have a maximum biomass density of about 0.25 pound per gallon(30 kg/m3), al- though some operators report achiev- ing maximum fish densities of 0.5 to 0.6 pound per gallon (60 to 72 kg/ m3). Vigorous aeration is necessary to dissolve enough oxygen in the water, especially in the warm water used for tilapia culture. But vigorous aera- tion re-suspends and fractures solids that should be quickly removed from the tank in order to maintain good water quality conditions. In systems where supplemental oxygen is applied and vigorous aeration is not used, maximum fish density can often exceed 0.50 pound per gallon (60 kg/m3), and some system designs routinely use a maximum of 0.75 to 1.0 pound per gallon (90 to 120 kg/ m3). For commercial operations, the expense of supplemental oxygen can often be offset by the significant in- crease in maximum biomass density

cheers

Yep, read that article before SolTun - Rakocy knows his stuff. Did you do the math ?

0.25 pound per gallon converts to 1.75 pound per cubic foot - significantly less than what his consultant is talking about.

The other part about "some operators report", ties back to my main point - you may achieve but that doesn't mean you can sustain it. With current knowledge/technology you're talking about a system finely balanced on a knife-edge. Even ignoring that, 0.5 pound per cubic foot is less than 5lb per gallon. 9 pound per cubic food is ludicrous.

If I was cnhman2008 I'd stop talking to this consultant and start doing some independent research to lift my base level of knowledge as I said at the start of this thread ! It won't cost him much besides a few bucks and some time, but it could save him a small fortune by assessing the project with realistic numbers.

Hi chllidude
No I didn't do the math, I have a general dislike towards high densiety operations with any species based in my view on animal/fish wellfare.

My post(link) was pointing out that what he aimes for is posible acording to the SRAC paper in the link.

So his consultant might know his stuff ?

I'w newer raised tilapia, so I got non experience to share here and would normally not have responded to this thread.

I did it afterall, because it is a new member asking a q, and when Charlie(mod) posted the hostile post, where he stated, he hope that OP fail his project (that it ended in the bin where it belonged) and that OP would be a person giving other BYAP members fals/wrong advice in the future.
I thaught it appropriate to show that OP and his consultant, have sientific suport in their goals, regardless of mine, and others view on the matter.

Charlies post have later been removed (moderated) lets hope the new member return

cheers

I removed my own post, SolTun. It was a result of too many beers and I agree it was wrong of me to post in that manner. Silly mistake to get on the computer when intoxicated. Apologies.

Having said that I still dont agree with the stocking density described for an AP system but we still dont have much information on what is planned.

Cool Charlie
I'm glad to hear, you removed it your selfe

Never heard of to many beers No stocking limits there

Yes I agree it's not suited for a common AP system, I read his Q more like he planned for using some of the waste from a intensive AQ system to grow some plants on site as a bonus or extra income.

cheers

Nope, that's why I asked if you did the math. If you convert the figures Rakocy used to the same units that cnhman2008 it indicates that the figures cnhman2008 is quoting are totally unrealistic. Reread my previous post.

Like you, I'm also against ridiculous overcrowding monoculture production like that. It's exactly the feedlot/caged production systems mentality that we need to eliminate.

What I'm also trying to do is get cnhman2008 to do some independant research and save himself a world of pain and regret.