So I've been building a reef tank for a couple years now and it was looking really good. I did a water change and I could see that my sump had seen better days. So I decided to clean the sump because it didn't look so good and I didnt want the wife to have a reason to complain about how it looked. I drained the sump and scrubbed it down. Looked nice and clean and was proud of how good it looked. I put it back into the system and did the water change to just the sump and didnt think anything of it because its not that big of a water change. Well I was wrong. As soon as i got it up and running I could tell something was wrong. My tangs started sitting at the bottom of the tank and all my coral closed up. I checked all the levels and everything seemed perfect. So I didnt think anything of it. The next day I could smell the bacteria had started to die in the tank and my water was cloudy. Instant reaction was to do another water change to help save my tank. That was another mistake. I looked at all the forums and I have caused my tank to go unbalanced. Once that happens there really is nothing you can do. You need to let it cycle again. All my coral have died and I have a couple fish still hanging in there. Biggest mistake I ever made and now I have to watch my tank die. I'm letting it get back to being balance but I have paid a huge cost. So if you are reading this. There is a such thing as cleaning too much. If you are going to clean do it in stages and nothing over the top. I'm happy I have a nicee clean sump but my tank is not doing good at all. Very sad lesson I've learned and one I'll never do again. yes yes yes I know I'm stupid.