Hi! I'm new here. I have a question. And one of my neon tetras in a school of 7 in a 10 gallon tank with 1 nerite snail has some fin rot. I don't know why. I immediately tested my water, and it came out 0ppm ammonia, 0ppm nitrite, ~30 ppm nitrate. I do 25% water changes each week, and I have cryptocorynes, and some vallisneria. I had this tank setup for about two years. Anyone have some ideas?