Biggest fish for a 10 gallon??

2 dwarf gouramis is a definite no - 2 of them need more space than a 10, and since only males are sold at LFS (females are only gray colored) and males tend to be aggressive to one another even in larger setups, it's not a good idea. A male and a female molly wouldn't kill each other, but you might end up with a whole bunch of baby mollies...I'm sure someone else can give you more advice about them though, I'm not a molly fan.
 
I'm pretty sure you can keep frog fish in a 10g, their quite unusal but then you would have to turn to the dark side and have a sw tank.
 
I'd love to to SW but I only have 3 years of aquatic experience.
 
I'd love to to SW but I only have 3 years of aquatic experience.

I know people with much more than 3 years experience who should not be allowed to keep anything. Its not how long have you been doing it but how willing to learn are you. I would say go for salt, granted 10g is a small tank to start into marine with, but take it slow ask lots of questions and be willing to listen to the answers. You are at the right place if you want to do this.
 
Awesome. Maybe I'll ease into it and start with a brackish tank.
 
I'ma have to give an adamant NO to the suggestion of sailfin mollies. Sailfin mollies top off at 4 or 5 inches if properly cared for and considering how important excellent water quality is to their well being, attempting them in anything under a 30G is not to be recommended lightly. A 10g is the perfect size for many uncommon livebearers, and a trio of most limias or goodieids would be a good choice. Also, microrasboras, CPD, everglades sunfish, or some of the smaller mouthbrooding bettas would all be excellent choices. Oh, and I almost forgot killies! Most of the aphysemoin/fundlopanchax species would fit well and are also an excellent starting point to get into killies.
 
Would 1 BN be OK? Or a school of small cories??
 
Plenty of your local fish would do well in a 10 gal; some of the moderate-sized madtoms (3-5") are probably the biggest natives that would do well in a 10.
 
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