I have had a rough start with the hobby of saltwater fishkeeping. I am the first to admit I went into this hobby blindly and listened to some of the wrong people without doing research for myself. I want to say thanks for the help I have been given on this site because a lot of information everyone gave me has helped me fix a lot of my mistakes. My water is now crystal clear and most of my algae growth problem has been under control. I still have a couple of questions about water. I am not sure how all this cycling business works and I am reading up on it today. If you look at my threads from when I first came to this site, you will see I had way too many fish in my 46 gallon tank. I have removed four of the fish and took them back to the pet store. The other day my powder brown tang suddenly died and now this morning my flame angle died. My water has been reading better than it was before and I am curious if or what parts of my water parameters could be deadly or if these fish just died for whatever reason. My water is Nitrite 0.1, Phosphate 0, Alkalinity 1.6, Nitrate 25-5.0, Ammonia 0.25, Salinity is a little high at 1.026. I am using a sump with a 1000 gallon per hour pump, a built in skimmer, a 9w uv sterilizer, a 10 by 8 floss pad for filtration which I change twice a week, the overflow prefilter I rince out once a week, my temp is 80-82 degrees with the light on and I am not sure what it is with the light off. So far I do not use a heater and was wondering if the tank is getting cold at night and the temp fluctuation is shocking the fish to death, but I know I keep the inside of the house at 74 degrees 24/7. Or if maybe the salt being a couple of points higher than what it should be (which I am changing immediatly) could be a problem. Thanks again and I appreciate any help. Bill.