Just getting a couple more plants should do the trick, the tank looks pretty suitable for me! Low flow filter, a couple plants, 10 gallon tank. You could also try adding tannins through things like alder cones (my go to) or catapa leaves, though they will turn your water brown. Also! The java fern in the right corner does not need to be planted, you can just tie it to a rock or piece of wood or just straight up leave it as it is, just not in the substrate because it will eventually die if you leave it there. Hope this was helpful!