Any tips for a new addition to the tank?

[freshwaterfishfan]

Hello everybody, I just wanted some tips or advise on what(if anything) to add to my tank. I have a 20 gallon tank with 1 crowntail betta, 11 neon tetras, and three mystery snails(more are spawning). I was thinking about some sort of catfish or a black Mollie.
Thanks in advance.

 

[xfactor6699]

I've taken a liking to harlequin rasborias like 6 they school great and the betta will keep them in check

 

[gkuzel]

A little shoal of Cories would be nice. They're cute little 'cleaner-uppers'.

 

[arangarajan93]

Ya, u can get a black molly!!

 

[freshwaterfishfan]

Okay, I was going to add about three cories and two mollies but I started seeing a lot of baby snails and algea. As a result, I got two clown loaches and a rubber lip pleco. Would i still be able to mix in a Molly or two?