Okay, things can get a bit overwhelming.
Lets just try to get the fish you have under control.
For now you may want to use both your 10 gallon and 5 gallon until you figure out what you are going to do.
The pleco will definitely become too large for a 10, the average pleco that you buy at the fish store, is probably a common pleco- they can be different shades of brown and such- may grow VERY large- like at least 1-2.5 FEET or probably more. The problem with the fish guy who says it is going to be 5 inches is that lots of fish stores put plecos in different tanks around the store. The pleco may may not be correctly labeled and the employee may become confused and just tell you something because they don't want to say they don't know, then be embarrassed.
After all, they are trying to sell you stuff. So, don't always trust them. Not that they're all totally unknowing, but some are.
So, the pleco definitely needs to go.
Bleeding hearts are a type of tetra. They are happiest in schools- they are just plain miserable alone, they tend to sulk, etc.
The male betta could live in the 5 gallon.
Guppies and platties are livebearers. Guppies will reproduce quickly. You said both platties are males?
If it is a true panda cory, it can grow to abot 1.2-1.5 inches. These make a nice catfish for smaller aquariums.
The inch per gallon rule depends on other factors as well. EX: A really fat 2 inch goldfish will generate much more waste than your bleeding heart tetra of similar length.
Really, you need to make a decision to keep, in the 10 gallon either livebearers OR bleeding heart tetra. I would reccomend the tetra because the guppies will breed, then eat their fry, and it will be just plain frustrating.
Then regarding catfish, the pleco must go, then either keep the panda and get him maybe 1 or 2 more pandas so that he has some of his own kind and isn't lonely. Ottos should also be in groups, and you probably don't have enough room for a group of ottos, and you definitely do not have room for a group of ottos and a group of pandas! (I have never had ottos, but as mentioned above, they need a group)
I think you will enjoy a tank with a small school of tetra (like bleeding hearts)
happily swimming around and then a few panda cories on the bottom of the tank- I have 3 in my 29 gallon and they chase each other up and down the glass and into my caves and constantly searching the floor for crumbs, etc.
Remember, if it is a true panda cory, it will probably grow to about 1.5 inches.
You're tetra would be happiest in a school.
It sounds like you probably have mass chaos in your tank right now, and thats no fun to watch and no fun for the fish.
You will definitely need to take some fish back.
A nice organized community tank is a lot more fun than a huge variety of fish creating mass chaos.
Good luck. Remember, you will be a lot happier with fewer fish that all get along and are happy and your tank stays cleaner. Better to have fewer than to overpopulate.
Just try to get things under control for your fish and don't get discouraged. Your fish need you right now.
:dance: