have a remarkably small bioload. One of the first professional setups I did was entitled "Childhood Dreams," -- it was a 38 with a school of ~200 neons. It was an ode to the "ooh-ahh" every child experiences during their first trip to the fish store, upon seeing the Neon Tetra
for the first time. Heh. Also present were a mighty forkload (that's 2.8 regular forkloads) of pygmy corys, some japonicas, ottocinclus, and later after some of the neons died off (14 month average lifespan is kind of a pity), a pair of Discus
. I maintenanced that tank from up till down, and I never had any problem with the bioload. Nitrogenous wastes were always well under control.
Anyway, enough reminiscing. Heh. Since most tetra like soft water and low pH, especially neons, any small, peaceful fish that will also get on well in those conditions is a prime tankmate. Since you only have 12 gallons to work with, you might consider swapping the pepper corys for some pygmy corys. They exhibit all of the same adorable cory antics whilst maintaining a size comparable to a fingernail. Heh.