Mysterious deaths

[beatle]

I've had a relatively stable system for a while, but in the past few months I've had several mysterious deaths. Back in early February I left town for the weekend on Friday night and came back Sunday afternoon. My gold head sleeper goby and midas blenny were both gone. They had been in my tank since late last spring. I had a bacterial bloom for the next few days and I never found them in my sump or the floor, so I'm betting the cleanup crew got to them. I never saw any signs of aggression or disease.

 

March 17th I got a heniochus diphrutes butterfly. He adjusted very well and was eating ravenously the first day. On the 24th he was stuck to the side of my powerhead. No signs of aggression here either.

 

Today I found my coral beauty dead on the bottom of the tank and being consumed by a few hermits. She'd been in my tank since early summer or so. Same story as the others, no sign of disease or aggression, great appetite.

 

I have no idea what's killing my fish. My water parameters appear to be sparkling: 1.026 sg, zero phosphate, ammonia, nitrite, or nitrate. Ph swings from 8.35 to 8.45, and temperature is stable around 78-79. I can barely grow any algae in my tank.

 

Here's my current stocklist:

 

Mated pair of ocellaris clowns

Red firefish

Purple firefish

Helfrichi firefish

Midas blenny (added 2 days ago)

Red mandarin

Fire shrimp

Mated pair cleaner shrimp

A few peppermint shrimp

Assorted snails and red/blue leg hermits

 

Any ideas? It's frustrating to pour money down the drain and to watch happy fish disappear for no apparent reason.

[CaptainRon]

Any stray electric currents in the tank? Alk, calcium and magnesium readings? I don't know how much they'd affect fish but could, perhaps, lead to other theories about what's going on.

[treesprite]

sorry to hear about your losses.