1/2"

I have an IM 50 lagoon, and I purchased a Varios 2 DC pump. The website claims that the pump has a barbed outlet at 1/2"-3/4", which is compatible with my 1/2" tubing for the aquarium. When I received the pump, the barbed outlet was in fact 3/4"-1", and the barbed outlet was not stuck together...

I recently purchased a Marine Modular 800gph overflow box (top-view of outer box pictured below). It has three 1/2" drain holes that fit 1/2" uniseals. I will these for a bean animal overflow on a 32g display and a 20g sump. I realize now, however, that the 1/2" drain holes are considered...

I'm putting together a 20G Innovative Marine Nuvo reef, and I'm trying to decide between 1/2" and 3/4" bulkheads for the return flow. I plan on having 2 returns into the tank. Is there a "standard" size for a tank this small? Thanks in advance.