With a 55 gallon you have a ton of options. What fun! Mollys, guppies, a gouramI or several honey gourami?
What is “bad” about your water? Maybe knowing that would allow us to help better? Can you do to a fish store & write down fish you like the look of & we can help you figure out what could work together. Do you want babies or not (that will dictate sex choices for the fish).
What do you mean your water is bad?
What are the issues with your water?
Someone on here can help with “bad water.”
Most any species are good with Platys; I have a betta with some Platys. And a H. GouramI as well. They all get along just fine and are seem to all be friends. Yeah, please clarify/define "bad water":...pretty please!
The only issues platys have is male platys will chase/threaten other male platys if no females are present.
Cory catfish would be cool, although you would have to make sure they get enough food. You could also try giant sail fin mollys, they up to six inches and the males have a cool sail fin on their back.
I think schooling fish
People are replying but you never explained this comment.
I have other suggestions, as i’m sure others do to but without an explanation of “bad water” we are hesitant to reply.