I sat up my 135 gallon it cycled.Added a damsel and she did fine for a hour or so,died in 3 hours,three more damsels followed and they died in three hours.Today I tried a bar goby he too was fine for about an hour,,started breathing hard at two hours and died by the third..I don't understand what is going on.I checked my water and even took it to be tested,,salt is at 23, amm at 0 nitrites 0 nitrates 0..My crabs are living and doing great I added some more crabs several days ago as well as an emerald crab and all are fine.Any ideas? I am so discouraged and I don't know what to do..Fish die in three hours,no more than two..I don't get it,they seem fine then they start panting and kill over..I know there is plenty of water movement..I have the sump and two power heads going..