How many of these platies can I put in a ten gallon tank?

I'm wanting at least one of each, but if possible I would like more. I'm thinking maybe one more different colored marble and possibly even a red platy too. But I need to know just how many platies I can fit in my ten gallon tank. If I have to, I can take the hi fin off the lit, but I'd prefer the rest. Would this be overstocked? How many can I have? I've never had platies, In the past I've had 7 black mollies in a tank, though I forget what size it was, it was smaller than a ten gallon. The tank broke. But the fish had die when my dad change the water while I was away… It tresses them out, maybe he forgot the conditioner or something but he has had a 50 gallon fish tank in the past so idk what happened. But when the water was changed they all died…

Anyways, how many platies can I put in my ten gallon tank? Do I need a heater? I have a water heater, but I've never used it on the ten gallon. I had used it for the Molly tank. Help? I need advice. This is just a plan for after my current baby bluegill outgrows the tank… No I'm not going to release him… Mainly because I just learned its illegal, tho I feed him fish fry out of the creek I got him from… I'll just buy him a special large tank just for him when the time comes. He's currently smaller than an inch so the tank he's in should be fine for now.

Btw, sorry the hand writing is so sloppy, I did this with an app on my phone and it hard… You try writing on a picture with an iPhone 4. See, hard.

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