I have a 55 gallon tank. I've never had problems with my levels till this week. My ammonia is 0 but my nitrates are extremely high. The color matched the highest level on the API test kit! I did a 30 to 40 percent water change yesterday before I realized my levels were so high. At the beginning of this month I hooked up a new canister filter. I added purigen to this filter even though I've never used it before. I left my Marineland Emperor 400 running and am planning on taking it off in about a week and half and moving the biological filtration component in it to the canister. I can't figure out why my nitrates are so high, maybe I'm overfeeding but I'm not sure. What should I do to get them down? I'm worried about my fish. My upside down cat hasn't been acting like himself lately, I haven't seen him eat in several days and I found one of my bamboo shrimp dead a few minutes ago right before I ran my tests. I was about to do another water change but wasn't sure if it was a good idea to do water changes two days in a row or if that would even help since I did one yesterday and they are still this high. Any help would be greatly appreciated!