My Nitrate was at .10ppm then a few days when i added some fishes and corals the nitrate went up to .30ppm I was shocked so i did a water 20%change every other day so far. I have a 25gallon tank but i think i have too many fish inside. I got a true percula, 5 cardinal, a dragon goby and a six line wrasse. with toadstool and frogspawn coral and featherduster. Everything is still alive and doing fine and i only feed them half a cube of brine shrimp and as for iodine i only use a little bit per week. How would i lower the nitrate besides water changes?