Now that my fish are getting larger( some are close to 10"), I am realizing that I may have too many fish in my system. I have a 275 gallon IBC tote for my fish tank draining into two 1' tall IBC grow beds. I have around 40 tilapia in the tank (I started with 30 and figured I'd add 15 more(mistake), and I have had about 5 get sucked into the plumbing when they were small). They are getting bigger faster now that the water is warm, but they are not quite big enough to harvest. I am having quite a bit of poo settle on the top of the media in my grow beds and I periodically have to mix up the media to keep algae from growing where the poop makes a puddle that holds water on top of the media. This is particularly bad in the first grow bed from the fish tank. When I first noticed this problem I was using a purina feed for catfish that was tiding me over until my Aquamax 4000 arrived at the feed store (which took two months for some reason). The change of food has dramatically decreased the amount of waste, but as the fish keep growing the waste is starting to accumulate again. There seems to be quite a few system that only use the grow beds for filtration and don't have a solids filter in front of the grow beds. So, how do you handle the poo.
Does anyone have suggestion for dealing with this increasing amount of solid waste in my GBs?
Is there any way to distribute the poo more equally to the two grow beds hooked up in series?
Do I have too many fish? I would hate to have to dispatch any fish before they are ready for harvest.
If I add more worms(I have only put about 25 worms in the system) will they be able to handle all this waste?
What are some examples of ways I could prefilter this poo?
Any help would be greatly appreciated.
1) If your 40 fish are near harvestable--approaching a pound or more--then this would be 40 lb. of fish for less than 20 square feet of growbed. If that's the case I'm impressed that your plants and growbed-biofilter are able to keep up. For that high a ratio, having a solids filter may not be such a bad idea to reduce the overall nitrogen load. Either that or you have some pretty heavy feeders going in your growbeds.
2) More worms could help. I don't think there's much risk in having excess worms.
3) By "in series" do you mean fish tank feeds bed 1, which drains into bed 2?
4) For solids filtration methods, a search on this site will offer up suggestions as well as debates on the pros/cons of removing solids. Check out Amy's fish poo thread on the Members Introduction forum.
The largest fish is probably close to a pound, but the majority are still around 3/4 pound. My biofilter seems to be able to handle the ammonia load fine its only the solids that are becoming an issue. I am afraid that I may be pushing the limits with this many fish, but I just hate to harvest them when they are not quite big enough.
Actually about 3 weeks ago I removed every plant from my growbeds (actually every plant in my 20'X60' greenhouse), because the summer has brought a huge white fly infestation. My laissez faire approach to pest control has proven to be completely ineffective, imagine that. The only plant matter in my system is the duck weed, which is also in an IBC tote that I had originally designed for a DWC bed, but I use the duckweed so much (it has become a staple for my chickens) that I have not put a raft in this tank. your questions made me curious about how the numbers looked so I tested everything this morning. ammonia is at 0.25, nitrite is 0, pH was 7.6 (I have an issue with hard well water so this is lower than usual), and the nitrate test showed an alarming color of red that is way off the chart, I can only guess that it is well over 200ppm seeing as how the test only reads up to 160ppm. The fish seem to be unaffected by the high Nitrate, but I am going to use some of my system water on all my citrus and other nitrogen hungry plants around the nursery to try and use up some of those nitrates.
When I say "in series" I mean the plumbing is in series, meaning it tees into one bed and then continues to the next bed. The majority of solids is deposited into the first bed. I was thinking of running a separate SLO line from my fish tank to the second bed to try and equalize the solids distribution. Either that or install a solids separator, before the first bed. Or maybe just harvest some fish...
Amy's thread was helpful, thank you
If your ammonia and nitrite levels are OK, then perhaps it is not yet a problem. You could wait for your fish to reach target weight.
If your worms lived, then they will reproduce. Might help to add more.
You might want to plant heavily. Roots will add more surface area for nitrification.