I currently have 13 fish in a 20 gallon long: 5 cardinal tetras 2 celebes rainbows 1 horseface loach 1 kribensis 3 lemon tetras 1 oto However, I plan on adding one more cardinal tetra, one more Celebes rainbow, two more lemon tetras, and possibly three more otos, and maybe three nerite snails or amano shrimp. For filtration I have a sponge filter rated for up to 40 gallons and an AquaClear 50 with the sponge and Matrix in it. I do weekly 40-50% water changes and I gravel vac every time. My nitrates stay consistent between 10 and 20. Should I upgrade my AquaClear and/or sponge filter and go one size up or will my filtration will be sufficient enough for all my inhabitants?