ok where do I start. I helped my gf set up a reef tank about a year ago. The tank is 110gallons, about 130 lbs of live rock, no wet dry filter ( I know I know) but I have had success in my system without a wet dry for years , plus we could not afford a wet-dry, so I went with the live rock and deep sand bed with lots of circulation methood, I did have a hang on canister filter. The tank was doing great for about 8 months, corals were thriving , the fish load was relatively heavy, we had a naso tang, yellow tang, several damsels, clownfish, a goby, lots of snails , hermit crabs, cleaner shrimp. Parametors were as followed, NItrates were always bellow 10ppm, ammonio 0, nitrites 0, pH was good but than one day out of nowhere we noticed all of the fish were breathing extremely heavy, I did the normal did a complete water test on everything at my local fish store and it came back as being PERFECT!! Temperature was fine, salinity was fine, but all the fish were breathing heavy, I did an emergency water change about 30 percent, it helped the fish stopped breathing heavy. The next morning the yellow tang and naso tang were on the ground practically dead, breathing extremely heavy, all the other fish were still alive but breathing heavy. I took the two tangs out of that tank and moved them to my reef tank at my house, the yellow tang survived the naso died. I noticed that whatever this was it affected the bigger fish more than the smaller ones, the naso was the biggest about 8 or 9 inches and it died, the yellow tang was about 6 or 7 inches. I did yet another smaller water changed about 20 percent, that seemed to help and everything went back to normal for about 1 month, I moved the yellow tang back to the tank and it was doing great yet again, another month went by and everything seemed back to normal, I got another naso about the same size as the original, everything was perfect or at least 3 months, than once again at a random time the fish started breathing heavy again, and again i did a water change and it got better the same day but AGAIN at night it went all bad the next morning EVERY single fish died. I am not a beginner I may use different methoods than some of you but I have been very successful for years, I cannot figure out what went wrong. Why at night, why does my water always test perfect , someone please help me ohhhhh I almost forgot, all of my coral have always been thriving during this entire ordeal, I also have a carpet and long tentacle anemone and they have been thriving, they do not seem to be affected what so ever, im very confused. The tank looks great but we have no fish, what should I do next? Please help.
