Soil bottom of 8"-1ft is plenty of substrate for rooted vegetation to grow well. Now with a couple of TGC,, you will not get any vegetation established in the pond. TGC will anything except FA that tries to grow. TGC will not eat that FA that you were dipping out with the net.
The big benefit of the tilapia is FA consumption and they will eat a lot of the FA and turn a significant amount of it into a large fish biomass so you can remove those nutrients that grew that FA out of the pond. Chemical addition does not do that. Ponds are nutrient accumulators and it is the wisest manager that removes some pond nutrients each year. You also did that prior using the Pool Net removal method.
