But be careful because flowerhorn are very fierce and do not mix around.. PLUS oscar are territorial, if that is an established oscar tank, the oscar will be intimated at the beginning, and may bully your smaller flowerhorns.
Make sure ur flowerhorn is at least half OR 3/4 of its size..
However, no direct answer.. you need to find out and observe.. I'm rearing 2 OSCARs, they definately are big bullies..