It is a bigger deal than you think. Tilapia are a much bigger fish and have larger needs. You have to keep separate water systems as somehow babies make it through any sort of filtration you can imagine, and adults are known to jump from one tank to another. Tilapia like Nile and Horonorum need hundreds of gallons of water to spawn reliably.

Just about every commercial grower that has tried to keep 2 species on the same property has failed after just a few generations due to cross contamination.