I have kept blue tilapia (aurea) in a fish tank at my house.

I still have a small 2" juvenile.

I had a 13" adult in my 75 gallon.

It preferred to eat stuff other than the algae and elodea in the tank.

Now I had a 5" juvenile in an outdoor patio pond and it liked lettuce and duckweed. There was still algae in the container.

I think they eat more bugs, zooplankton and plants than algae.