1. It is never a good idea to hand freed a Lionfish. No matter how tame you think your Lionfish to be, they still have very venomous spines and should never be hand fed.
2. When adding particularly aggressive fish to your aquarium, it is a good idea to move around the rocks and such in the aquarium before placing the new fish into the aquarium. Moving the rocks in the aquarium will allow the fish to go back and stake out their own territory.
3. It is not a good idea to wash your filter media with regular tap water. The tap water can kill the beneficial bacteria that is built up in the filter. Use distilled water to clean out your filter and its components.