My personal opinion is that you're fairly heavily stocked for a ten gallon already. I'm not sure what your filtration is like, nor how often you do water changes, but if you're wanting to add some bottom dwellers, how about a few otocinclus cats? They stay very small, they're cute, and they're good little algae eaters, too. I would get at least 3. If you want to keep that many fish in a tank that size, however, I would recommend dual filtration and twice weekly water changes.
Btw, you said your tank has been up for a month; did you do a fishless cycle first? If not, you're probably not finished the cycling process and should definitely not add any more fish for at least a few more weeks.