5.5 gallon Tank with female betta and 2 ADF, additions?

Ideally, you can't add anymore fish. Decorations? Absolutely! Well really, one more "fish" you can add to your 5.5 gallon is a single snail. I don't recommend apple snails, they get huge! Other than adding a snail, that's it. I also suggest adding some live plants. They look great and help maintain a nice fish tank water balance.