I have read several times on the forum where people have complained that they stocked tilapia, but they didn't even make a noticeable difference in their FA. However, they may have stocked too late for the next generation(s) to make any significant dent in the FA?
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Rod I am short of time to answer the rest now but will try to get to them this evening. BUT to answer the above question, I have found out that you HAVE TO kill the FA 4-5 days prior to a week post stocking the tilapia or they CANNOT eat all the old algae AND the new growing crop. Even at 100#/acre they cannot eat both old and new. Been there, done that in my pond. I use my personal pond as a test pond that way the owner can't get that upset with me.

At 40# per acre 50/50 M/F if you kill the FA, they can keep up with eating the new stuff. If it's really, really bad you might have to treat it once or twice more that year, but that also depends on the water clarity and pond depth. If it's a 1 ac pond with <36" visibility (secchi disk) then they should be able to keep up with the new growth IF the tilapia stocked are 50/50 M/F.