How many new tank mates for tetras?
 

I have a 20 gallon tank that currently occupies 2 glowlight tetras, 2 black skirt tetras, and 1 bristle nose pleco. I'm planning to add either a couple different species of danios or a couple paradise fish and some neon tetras or a combination. I really want some color in the tank and would like a decent size school, but I'm not sure how many more fish I can add or how many more species. Any advise?

as long as you have a mature aquarium (biologically speaking) you should be able to add about 6-7 neon's total but no more than id say 2-3 a week or until your levels even themselves out.

First you need to add more of what you have. Characins (tetras) are shoaling fish that live in groups and will be better (healthier) if kept in a group of 6 or more, always. Adding 4 glowlights and 4 blackskirts will still leave room for another tetra species; if you don't particularly want more of the existing tetras ask the store if you can trade them for other fish. It is imortant to always have tetra species in groups. They will interact and behave naturally, which is more interesting to watch, and they will have less stress which means better health.

Byron.

Aye, what byron said.

Tetras need to shoal, in fact I'd say thats the whole point of them! If you want pretty, non schooling fish there are far more interesting options (behaviorally and physically).

What are the dimensions of the tank? Volume can take many shapes. My 120 litre is massive in fish terms compared to a cube.

It's 10 1/4 wide, 20" long, and 11 3/4 tall.