when i had damsels in the tank cycling it, none of them died until 1 month later ending the cycle. 2 died. Water params were all 0 except nitrate was b/w 5 and 10 ppms. I do use tap water and condition it for top off. I am just wondering of the cause of death was more than likely chronic stress over time. They looked healthy as ever and just got lazy one night and died. I notice they all seems to stay near the heater at night and thats where most of the detritus builds up. Theres enough water movement everywhere alse. Is it possible dead spots, especially if popular to sleep near can break down the fishes immune system even though the readings are saying everything is safe in the tank overall? I noticed when removing the fish, one eye was bulged out. Not sure if this is an indication of one problem or another......Opinions

build your rocks up so the fish have a place to hide..if there is not a lot of circulation in one area. you should try to increase or move powerheads to get to thoses area's..is it possable to overdose water conditioner?what is your ph at?

ph looks like its at 8 on the dot..if i am a MJ 400 in that corner im afraid it will blow sand everywhere, but i ordered it yesterday..and there havent really been any acute changes in any params over the month time frame and no disputes occurred b/w fishes...I have not heard of damage caused by conditioner....

not a criticle issue but i would raise your PH to 8.2 - -- 8 is ok but you don't have much room if you do have a drop for it to be dangerous . . I had a PH drop after my first cycle and lost 2 damsels {not saying that was it but mistieriously died one night exactly the way you explained it, so who knows - - -thats why I did a fishless cycle the second time and things seem to be fine - - i boosted my PH with a product called Marine buffer 8.2 {MADE BY SEACHEM} one table spoon a day disolved in a cup of water for a week and it was right back to 8.2 - -there are all kinds of buffers out there - - up.....down....8.2, 8.0,8.3 etc etc . .Boss

could very well be - -im not familure with that drastic a fluctuation just over night {but I have been known to be wrong, lol} only reason i say that is ...when you use a buffer to raise PH it takes like a week or more to get from 8.0 to 8.2 so i wouldn't think it would swing to crazy over night - - but also like i said....i have been known to be wrong before [ssshhhhhhhhhh, you guys are the only ones that know that though..LMAO]

a thought on the powerhead - -i wouldn't think one power head would caause that much heat .....UNLESS.... it's dirty, clogged or failing....that would cause the motor to "drag" and make heat - - -any of these simptoms are bad....one, over power consumption, two, over heating, three - - - in a bad failure the possability of electrcution is possable = bad for you and bad for fishies....be careful ...Boss

see....told you i could be wrong...damn Pimp always pulling the carpet out from under my feet .......LOL