Yes, fishes is correct English for multiple species of fish in one area.
I have four neon tetras and three zebra danios in the tank now. It’s still very bare, but I’m getting there. I should have the tank planted by next weekend. My local fish store is bringing in some plantage for me.
Then I’ll add more danios (maybe the long fin variety, they are very pretty) and finally more tetras. I like the idea of having more fish than one or two ‘showcase fish’. The tank seems more natural to me.