I have a +/- 600 gallon tank with tilapia that has gone quite green. I have tried covering it, feeding the fish less, etc. Nothing is clearing it up. I think I need to do a drastic water change to clear it up, but want to know how far I can push the change. I have about 35 tilapia in the tank. Any advice would be appreciated.
What are your nitrate levels at?
Oh, and anytime you want to do a water change, go for 1/3 of the water. And make sure the water you add back in doesn't swing your pH.
Get yourself a couple of cat fish who love to eat algae :D
UV helps control green water. A 15w UV would work good for a system your size.