unsuccessful tank

[cheets22]

I have a 20 ish gallon Saltwater tank. Fish only. And I originally bought some fish, had everything being monitored and then all of a sudden all the fish died within two days. my levels were all fine. Then just recently, I reset up the tank, let it cycle, then added one domino damsel. it's been up for about a month and now the fish is dead. what is happening to my tank? please help with any suggestions for my next setup

 

[lefty]

Hmm. What kind of water did you use? What was your salinity at? Are you sure that no contaminants got into your tank somehow? Did all the fish look healthy? What exactly were all your levels at?

-lefty

 

[cheets22]

its actually my friend's tank that I am helping her with, so I am not sure of the exact levels. She was only feeding the fish every other day, which I thought might be a problem. she originally added dechlorinated water when she filled the tank, and now she has refilled those bottles let the water sit and then poured that in as necc. is it true that the water dechlorinizes when it sits after coming from the faucet or should something be added.

 

[sammiefish]

yeah, you have the choice of letting water sit 24 hours then using it or using a dechlorinator additive... either way... no more chlorine... If she was using RO/DI then it should be chlorine free at the hose...

 

[ophiura]

How are you cycling these tanks, and what water parameters were you following? Did you also get the water checked at the LFS for verification? Just that with them dying withing the first month - tanks often cycle in 6-8, so looking at an ammonia issue would be logical.
Feeding a damsel every other day is not, IMO, going to kill it. Feeding it too much every other day could though.
The other considerations are any cleansers in the area, on your hands, painting, carpet cleaning....

 

[mudplayerx]

Much more info needed.
Need weekly tests of:
PH, Ammonia, Nitrites, Nitrates
Also, what temperature is the water? Where is the tank set up?
What is she feeding the fish? Is she using at least 3 different fish foods?
Is she using anything other than water/vinegar to clean parts of the tank/equipment?