Personally as someone who has a bicolor I think it would be a bad choice for a FO tank without lr. Mine spends a bunch of time picking at the LR for food, and for the first month that's all he lived on. No LR, no fish after a few weeks in my opinion.
Good choices....
Single fish or 2 - dwarf lion. Not much else springs to mind as preds tend to grow v quickly. Hard to imagine keeping a trigger for v long in that tank.
Reef - Clowns, damsels (if you must), chromis, gobies (some), blennies,smaller hawks, cardinals, smaller wrasse, smaller Centropyge angels, pseudochromids, grammes,chalk bass.... and tons of others.
If you don't care about inverts Valentini puffers are quite amusing.