,,Definitely no yellow tang, they need a lot more room. Eels are messy predators. Snowflakes are crustacean eaters so I doubt it would go after any reasonably sized fish but it would definitely eat shrimp and crabs. Plus they're super messy fish. If you are focusing on corals mostly I'd stick to clowns and other small reef safe fish like gobies, blennies, cardinals, small wrasses, etc
20 Gallon SPS reef
29 Gallon FW "fat catfish" tank
20 Gallon Long Dart Frogs "Zig" and "Zag"