The "Ick" I saw, mostly on the velvety black Mollies, was in the form of cotton balls on their bodies.
I rarely saw it on any other freshwater species.
Wish I could comment more on salt water fishies.. Sounds expensive.
Never had a tiger barb "eat" my neons or cardinals or any other fish. Just eeemed to like ripping off tails. Probably a territorial thing. Still not suitable for a community tank. He was a menace to the community. I didn't know. Had he just been having sex with the zebra fish spawn, it would have been tolerable, but nipping off tails of the pillars of the community was too much to tolerate.