:'( last week I lost 5 fish in as many days !! One was a rubbernose pleck that lfs sold my husband to go in with my gsp--he died.Maybe from brackish water ?? Also, in my 55 gal I have african cichlids who have all been doing great for well over a year now. Well per routine I did a 30 % water change and vacuum. @ days later my blue hap moori was missing so me and hunny go looking and found him under a rock ! SO we assumed that the rock slipped and he became stuck. we were really sad--one of our favs ! The next day my husband asked where peewee was--i looked ...stuck to the filter/pump thing...dead !! What is going on ??!! I see no injury, no signs of disease so i check water parameters-ammonia 0, nitite 0, nitrate 10, ph 7.6, temp 76. I have noticed any unusual aggression, etc. yes i did add prime during water change. At no time did I notice anyone behaving odd-gasping for breath, swimming to top, swimming funny--nuthing!! The ONLY thing that i have noticed is 2fish almost acting as if they are holding eggs--opening and closing mouths frequently at bottom of tank,doing some little dance thing,etc. any ideas of what could be going on ???