There are a limited number of species that can go in a 5 gallon. You can do a single betta OR a small schooling fish, such as a celestial pearl danio or another type of microrasbora. Tetras, danios, most livebearers, gouramis or any other sort of community fish are unfortunately out of the question.
You could supplement whatever you decide to do with a few snails and shrimp as well.
Have you completed a fishless cycle?
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