IMO the tank wasn't overcrowded to begin with, however it does need more filtration... I think an Aquaclear 500 would be barely sufficient for a 55, but I prefer to overfilter if possible. Anyways that's my two cents.
And weather loaches are awesome, I'd get a couple but my tropical 55 is strictly Amazon fish (well except for the ghost shrimps, but those aren't exactly fish...)