First off, welcome to Tropical Fish Keeping forum.
Before adding, I would consider removing, or preparing to.
The Raphael catfish can reach 9 inches, though around 6 inches is usual in the aquarium. But even at this, it should have more space, a 4-foot tank minimum, to develop and live properly. It may eat small fish, and being active during darkness will have the advantage when it decides to.
If you like the Head & Tail Light I would increase the group. On their own, two may turn nasty as they mature. This often occurs in shoaling fish that do not have a sufficient-sized group.