Can a little pH fluctuation kill a fish?

[TDesaulniers]

So, I have a small to medium sized koran angel fish in my 110. I have had him for about two months now. He use to be very active, curious in nature and always eating. I am now really worried about him because he has a disinterest in food, seems skittish and really doesn't come out from the rock structure. I have been keeping up with all my water changes. My test kits are expired so I will have to buy some new kits. In the mean time though, what could be causing this? I have 4 RBTAs in the tank. Do you think maybe one of them stung him?

The reason why I ask about the pH is because I was on the phone with one of my reputable LFS and the employee on the phone was either saying it was an electrical leak and to get a probe and test it or it was the pH. I then said well wouldn't both of those affect all the fish in the tank instead of just singling out one? He was really sure it was the pH and I was under the impression that a little pH swing would not kill a fish. I would expect my derasa clam to go down before a fish would.

This exact situation also happened to my yellow tang about a couple of months ago. The tang was active and healthy and all of a sudden, stopped eating, hid in the rocks and eventually died. This time I want to fix the situation before I lose a pretty fish.

I'll be getting the water tested tomorrow. Please help. Thanks!

[dzhuo]

This exact situation also happened to my yellow tang about a couple of months ago. The tang was active and healthy and all of a sudden, stopped eating, hid in the rocks and eventually died.

This is very typical of fish infected with flukes: Mysterious fish deaths are more common now (Flukes) (http://www.reefcentral.com/forums/showthread.php?t=1260067). Have you rule out this possibility? Are your fish QT?

pH fluctuation is probably not the cause of your fish's death.

[TDesaulniers]

This exactly the symptoms of my fish. Thanks so much!