how many fish
 

Hello, I have been looking at my tank and feel I could add a few more fish. I was going to add 4 neons and 3 head n' tail tetras, what do you think?

20 long planted
8 neons
3 head n' tail lights
2 corydoras

Instead of adding more neons, I would add the head and tail light tetra, and another cory. Don't add them all at once though, since you're getting pretty close to your max bioload.

Thanks for the help, I will most likely pick up 3 head n tails since my LFS has a buy 2 get 1 free deal and then get the corydora another time.

That will work fine. Later with the additional cory, I would get 2-3 more. A group of 5 is good, and you are OK in a 20g long with the other fish. But you will then be at max. The corys can be same species of mixed, if you have 2 of one species now. you could add 2-3 more of the same, or a different species, but if different make sure the 2-3 new are the same species themselves.

Byron.