Freshwater shrimp, crayfish, prawns – whatever you prefer to call them – are an excellent addition to an aquaponics system. Not just because they offer you a new form of food, they are a system asset. Prawns do a tremendous job at keeping your water free of debris when they’re in the same tank with your fish. Tilapia won’t leave them alone though, especially when they’re immature.
Some people pile up rocks and tile to give the crayfish a place to seek shelter. That’s fine if you’ve only got a couple of them and a small fish tank. For a bigger tank it takes more crayfish to keep the system running cleaner, and that piled rock method won’t work when you’ve got a deep tank. You have to remove all of that to clean the tank or catch your freshwater shrimp. Time consuming. Limited living space for those delicacies.
Crayfish shed their shells as they outgrow them, and during the time between the new shell forming and the old one falling off they are super vulnerable to their own kind. They grow really fast, so they need privacy pretty often. Like any species the big ones pick on the little ones, which isn’t good for successfully growing small prawns into full grown dinner-sized specimens. Then there’s the problem of them escaping their tank altogether.
Obviously, you have some issues that beg a solution here. I found this video that covers all of them in one easy step. You can house more prawns in a single tank if you give them high-rise accommodations that at the same time protects them from the tilapia overhead, and gives them all plenty of spaces to hide between shells.
Pretty nifty idea from Chris at Grow Dinner urban aquaponics farm in Statesville, NC. They raise and sell both tilapia and prawns. Check out his engineering. By the way, those are Giant Blue Claw freshwater prawns (Macrobrachium rosenbergii) he’s showing in the video.