I have a 20 gallon aquarium that is pretty well planted. It contained 8 serpae tetras, 4 false bandit corys, and 3 otocinclus. Today i decided to add two dwarf gouramis. I had hoped they would occupy the upper region of my tank some and i thought it would be nice to have something a bit larger to draw attention. So I did a little research (apparently not quite enough...), bought the fish, drip acclimated them, and sat down to watch. They hung out in my plants for a while, but quickly decided to look around their new home. Almost as soon as the serpae tetras saw them they started to nip at their fins. I considered taking the gouramis back after I saw this, but i have started to consider taking the serpaes back and getting a different kind of tetra. Any input on this descision would be nice. I would also like to know if anyone has any suggestions to replace the tetras with, and how long the gouramis can safely be left in the tank?

Serpae tetras are fin nippers. Instead of South American tetras, I would use rasboras, specifically Harlequin rasboras, which like the Serpae are also schooling fish, but not fin nippers.. Dwarf gouramis are great fish. Mine always seemed very curious and watching them breed, building the bubble nest is pretty cool..

That's exactly what i was thinking. The gouramis should be fine in there for a short period though right? Also how many rasboras do you think? 8 like the serpaes?

Personally, I would get rid of the Dwarf Gouramis.

Dwarf Gouramis, in most cases, will fight to the death once they establish dominace in the aquarium. Basically they are like bettas. Plus 20 gallons is just not enough for them both to be in there, at least with your current stock.

And that's the Serpaes nature. Mine were so aggressive that they were just fine in my Tiger Barb tank, fended for themselves.