Backyard Aquaponics
A place to discuss aquaponics

Appx 3-4 weeks in. Currently have appx 220 fish, 100 feeder goldies, 120 tilapia(1-4" size). System is cycled, with Nitrites at zero. I was planning on adding 300 more fish this week. They will be larger 5-8" size and the idea is to put them in 1 of the larger(1000gallon+) grow out tanks. Then monitor and start my breeders going to stock the other tanks. Does that sound like slow enough stocking? I started feeding more heavily the last few days, and nitrites and ammonia are both at 0. I could add another 1000, but I think in a new system, I'd be risking a crash.

Filtration information, volume and surface area? Anything else you can think of that someone might need to tell you the answer to the question? I'd definitely go easy considering you've just gone through cycling. 300 5 - 8 inch fish (what kind and how big are you growing them to?) seems like a lot to me but If you're confident that you have overkill on the filtration and your bacteria are pretty well built up, then go for your low end just make sure you've got plenty of aeration. Hopefully you have a quarantine system they can go in before adding them to the main system. Watch for spikes in ammonia and nitrites because they sometimes happen early on in a new system.

Theres not too many RAS experts here, Coach.

And even if there were you're not doing it exactly like the systems that are being run commercially so I don't think some of their numbers would apply. You'd be overstocked and could have a lot of fish die. Experiment a bit with what you can do and keep tabs on the system pretty close for awhile. This paper has an estimate for stocking in RAS but I think it's overly optimistic for a system that's new and hasn't got the bugs worked out and may not be designed to their criteria. Just saying buyer beware

http://ag.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop%20PP%20%20&%20Misc%20Papers%20Adobe%202006/4%20Culture%20Tank%20Design/Culture%20Tank%20Design.pdf

I don't know how they take the filtration into account but it's been awhile since I looked it over. Some biofiltration media tell you how many pounds of food they can handle based on surface area. If you happen to be using one of these, taking growth into account and allowing for them to overestimate you might come up with a reasonable number.

Cheers

Thanks guys. Filtration is 2 - 265 gallon IBC- 1 with appx 650-700 sq ft of shade cloth filter. 50-60' x 12' folded/jammed into one IBc with a lid on it. That's the final polisher. The mbbr is appx 10- 5 gallon paint strainer filters filled with plastic shavings. They are kind of neutral buoyancy and I try and keep them pushed around, since the aeration has a tendency to make them rise above the water surface. I had planned on a separate quarantine IBC, but couldn't figure out how to plumb it. I guess I could just aerate and keep changing the water daily for a few weeks. The tilapia source is the same I used for the 120 a few weeks back, so not as worried. The plan is to have around 4500 fish total when fully stocked, but I think backing that down to 3000 is better. 1 per 2 gallons is safer and I don't have oxygen, just the 1 HP blower. I think I'll get the 300 and monitor closely.

Hi
To misquote one of your fellow Americans.
There are unknown unknowns and known unknowns.
A known unknown is that without a suitable quarantine system in place .You will introduce problems in the future.
Please think about it.

Certainly a possibility Titus. But, once these fish are in, my expectations are that I will then use my own breeding stock and keep it a closed system. Since the fish that I currently have come from the same source and are only a few weeks from being introduced from said system, I don't think the risk is very high. That, and the fact that I could easily remove the feeder goldies(isolate) and then salt to 6-7ppt if needed for any pathogens. tilapia are wonderfully hardy and adaptive creatures.

Maybe give them a high concentration salt dip before putting them in the system. Might want to try it on a few first and see how they do before doing the whole lot

Dip for parasites - 30ppt - .5 to 10 minutes. Remove fish showing signs of distress immediately (laying on side or erratic behavior for example)

Good idea Scotty. I'm going to pay for 500, and pick up half that many. Still get the discount and let the system get used to the new load gradually.