I used to have a ten gallon tank similar to that. I used it as simple fresh water, fish only tank. I kept a couple of goldfish that were pretty happy in there for about seven years or so. At one point some zebra fish that were also pretty happy, I had a loach at one time too that must of lived for about eight years I think.

You can probably do okay with a couple individuals from one or two species. Maybe up to five individuals if they're pretty small fish. Although there's only so much that overhead filter can handle, so you may not want to put too much biomass in there.

Mm you can super charge your filtering out with more medium and plants and I do have a nitrate anaerobic filter.

Oh yeah that can help too. I guess it also depends on how often your willing to change the water, if there's any extra care you have to do for the plants, and if you're looking to have a wide variety of tame fish or a couple bold individuals.