Suggestions

[jm1212]

try here for some more suggestions

 

[cmazz70]

If this is an Eclipse 12 gallon you may want to forgo getting neons and Rams as they will all hang out near the bottom leaving lots of empty space above. You might want some fish that swim in the middle and upper waters. Harlequin Rasboras would be pretty good at filling out the tank, better than most small tetras. Six Harlequins and 8 pygmy cories would be one way to go.
Silvertip tetras are one tetra that will swim all over the tank and are very active. Or male Endler's livebearers. You could put in lots of them.
A dwarf Gourami will also swim all over the tank.

It is an Eclipse 12. You think I can have that many in the tank. I never seen those Endlers before, they're cool. It sounds like I would have more options with the harlequins rather the neon tetras based on their preferred water conditions.

 

[cmazz70]

4-6 would be nice depending on what else you get. Is this a tall tank?

The tank (Eclipse 12g) is about 15 inches high. What complimentary fish would you recomend?

 

[gmh]

If you like catfish you can put in quite a few provided they are pygmy cories, which only reach an inch or so in length. Corydoras Hastatus is my favorite pygmy as they swim in middle waters more that most. They can be hard to find however, at least where I live.
So 8 pygmies and up to 6 harlequins is quite doable I think provided the tank is properly cycled.
Endlers are very small, especially the males. You could put in up to 20 if they were the only fish in the tank.