Hello, I'm pretty new to goldfish care, and I'm having a bit of difficulty figuring some things out. I have two small goldfish, one celestial eye (Noodles), and one comet (Ketchup). I know I shouldn't have mixed them since one is a fancy and one is a comet, but they have been living together for a few weeks and are doing very well. They both eat well (not too much) and they don't seem to pick on each other at all. I also a a snail, who sadly keeps falling over and is unable to right himself. My main concern is the levels of nitrite in my tank. I am doing a 30% water change every 2-4 days, and testing the water every day. My ammonia is zero, but every time I test for nitrite it's above 2 ppm (mg/L), even close to five sometimes. I'm doing everything I can think of to lower the nitrite content, but nothing seems to be working. I've been thinking of getting a shrimp, hoping that it would help with the waste clean-up, but I don't want it to produce more than it helps. My two goldfish are about an inch long each, maybe the comet is 1.5 inches, and they are in an aerated, 20 gallon tank with a filter rated for up to a 30 gallon tank. They have a bit of gravel in the bottom, but you can see through it to the glass everywhere so there's not much problem cleaning it. I have a few fake plants and a hollow log structure (also plastic) for them to play in, but also a lot of open water. The tank is unheated, but generally about 70 degrees, and I have a scallop shell in their tank that I put food in so that it doesn't fall through the rocks so easily. I feed them frozen brine shrimp occasionally, but generally sinking pellets. I did a lot of research before getting them, and even though I ignored some advice that I know I should have taken I really love my fish, and want to do what's best for them. If anyone has any suggestions as to how to lower the nitrite content, whether it be with live plants, shrimp, or anything else, I would really appreciate it. Thanks for your help!