You probably shouldn't put a betta in a tank with a Penguin 200. The current could do a number on it's fins. I frankly don't care for HOBs of any kind in a betta tank. Were I going to keep a betta in a 20, I'd either get an internal with an outlet I could point at the glass, or a small cannister filter with a spraybar (like the smallest Eheim Ecco filter).
That said, a nice, colorful (if pricey) set up would be a male betta, 3 albino bronze cories, and a school of 10 espi rasboaras (or harlequins if you cant find espies).
Failing that, get 3 male and 5 female guppies. You will be flushing or freezing fry, though.
Do not mix bettas and guppies. Bad idea. Male bettas can go into kill mode on male guppies because of the fins. Female bettas are better by degrees, but can have the same problem.
If you can find good ones, a tank of 6 to 10 female bettas can be gorgeous.
Originally Posted by mcdanielnc89
I wouldn't get the betta if you get neon tetras... Neon tetras tend to be fin nippers and will more than likely nip your bettas fins...
Not so much if you keep them in a school of 6 or more. In a 20 high, bettas and neons would get along fine, as the betta would stick to the top of the tank and the neons to the bottom and middle. In a 20 long that could be more of an issue.