is this fish tank overcrowded?

You could still add another guppy to the tank without any problems.

I would actually add some bottom feeders like 3 cory cats

Your 10 gallon tank is already over crowed, it fairly is probable one rationalization why your fish stay in one place. So no you won't have the capacity to place 7 greater fish in that tank, if something you will possibly desire to take out a number of those fish and placed them right into a sparkling tank. Or supply them to a sparkling first rate living house. additionally, definite your 30 gallon fish tank is over crowed. That Betta should not be in there, it would desire to have that is very own tank. finally, you need to place your Betta's in a similar tank so as that they are going to combat. . . in case you opt for to be a murderer! the two Beta's will combat to the dying. desire this helps!

You're stocked for a 30 gallon right now. Mollies need to be in groups of 3. You need to get rid of some of those fish.

That is not over crowded at all i have a 20 gallon with alot more fish than that and they are all doing fine you could add some more if you wanted to like some bottum feeders or guppies or tetras

Your tank is currently 95% stocked adding the extra guppy takes it to 99% according to aqadvisor.com

Yes that is very crowded I would suggest a little method i used to reduce the population of my fish.

I went outside and pulled off a branch and then i carved the branch into a spear and ran around my house in a loincloth and a spear and started spearing the fish that i deemed unworthy of my presence and offered them up as a sacrifice to the Egyptian sun god Ra.

Its a effective method of reducing the population.