how many fish are you supposed to have to have a healthy 40 to 50 gal.aquarium?

It depends on the species of fish. What kind of fish were you interested in having? There's really no mathematical formula to tell you, as much more than overall body length come into play when stocking a tank.

You'd probably be better off getting a few more somewhat aggressive SA cichlids. Even though it's scared now, if you add another fish it may bolden up and attack it. You want things that can defend themselves, like a slightly larger firemouth or acara. You can probably get a shoal of giant danios or silver dollars.

You're going to hate me,

read up more on discus, they really don't go well with very many things and require a large tank, 50 wouldn't work forever. They're so sensitive and expensive that people take them super seriously. You'd have to get rid of the convict too.

angels also won't go with the convict, scaredy cat or not.

Keep thinking, either one of those fish is worth keeping with appropriate tank mates.

I'm 57, soon to be 58 and I truly believe I haven't aged as much as some people have because I've stayed very active. I still run, snowboard, hike, backpack and climb. I realize I've been blessed with good genes but the old adage "use it or lose it" is true.

Personally, I think you'd be fine adding some discus, or a fire eel, so long as you're sure those species can live together... ;)

somewhere between 1cm and 2cm per gallon so it depends on the size of the fish

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