Backyard Aquaponics
A place to discuss aquaponics

Depends on how big the catfish are

Thanks, I guess that wasn't a simple question. I am raising Talapia, AP is my life now, I am here all day and by the systems, I have had a fairly good experience until a recent spurt of deaths and my ammonia levels which where always .2 or lower swung up to the green color on the chart. I figured I was over feeding and overstocked with fish, so I harvested some and got the tanks down to about 30-40 fish in each tank of various sizes from 2" to 7". My water quality looks much better and the reading on the ammonia are @.2, the nitrates go up to 20-30 then back to 0-5 , I have no nitrites. Is my ammonia level ok at a steady .2 reading almost every time I measure it? and my ph is about 6.5-7.0 if it gets lower then I buffer with lime, is that ok or should I use something else to buffer it up?

Sounds like something is failing.

Pictures would help.

Sounds like you've done the right and smart so far. You've seen a problem and reacted, that's good, and you've sought out ideas from people facing the same type of issues.

Taking some of the biological load off the system by harvesting some fish was a smart move and reduced feeding is good when you spot a problem and need some headroom and time to find the problem and fix it.

I agree with Stuart some pictures always help visualize your system and spot potential design problems.

I not sure that there is something failing but rather too many fish but without seeing some picture and specification to open out the view, it's hard to tell.

Keep calm, it's a saying around here that your not a real fish farmer till you've killed some of your fish.

I saw a video from Kansas State U. A grad student there I believe. He said the UVI model was 60-100 gms per day per sq meter of GB. In my system with 15 sq meters, it would equal 300 grams on the low side of equation. Fed 3 times daily, I'm shooting for 3.5 ounces each feeding. Again, the formula is based on GB or FRC bed surface area.Not sure if this is accurate, but he had done his thesis on this and had 3 identical, scaled systems to run comparisons on.

First the UVI system only has DWC (which Chris referred to as FRC) not GB and they removed solids. Some were reintroduced but their method on how this was done is not detailed clearly in any of the literature that I have seen. So while it is good to know their ratio its not very useful unless you are going to duplicate their method which will be hard since it is not terribly well described when it comes to their solids treatment.

I think the grad student duplicated their entire system...scaled down. He has settling tanks, and fish netting, and spoke of remineralization process as well. Don't know if he has visited the UVI system, or just where he got the info. His primary thesis was regarding artificial lighting. Types and results vs cost? It's long video, I have only had timer to see parts of it.

Got a link?

Especially if they detail the MT that would be good to see.

https://www.youtube.com/watch?v=gTg3eQZaR5E

Kentucky State...my bad