HI guys, this is my first time actually posting on this site so bare with me! I noticed it was time to change my filter, when I went to change it I saw that the bigger filter needed changed as well so I changed both of them, a few hours after this is when I noticed that my nitrite and nitrate levels are high in my freshwater tank. I have tried a few different things now to get them lowered with little success. I have a 10 gallon tank with 5 serpae tetras and an emerald cory. The tank is about two or so months old. All other levels are fine in my tank except the nitrites and nitrates, I did a little research and decided to try a 30% water change, this didn't change the levels at all, I then decided to not feed my fish for a day(someone told me they would survive a day or two without food), this lowered the nitrites from 20ppm to 10ppm. I checked my water levels this morning and the nitrate has gone down but the nitrite is still at 10ppm. All my fish seem to be doing okay, my Emerald Cory gulps for air every so often but not more often then normal and my tetras are acting normal as well, I need help fixing my water before my fish get sick! Thanks for all the help in advance!