Clear box of dead fish.

[ChrisOz]

A lot of these suggestions need to take into account the fact that his inverts are doing fine... inverts with open circulatory systems that would, theoretically, be more apt to kick the can if some sort of contaminant was in the water. I'd maybe consider internal parasites as it doesn't sound like there's anything externally visible that might be wrong with your fish. That, or your girlfriend hates your hobby and is secretly sabotaging you. It's interesting that you've never been present when a fish disappears or dies...

Probably disease though.

 

[Mastermind]

That, or your girlfriend hates your hobby and is secretly sabotaging you. It's interesting that you've never been present when a fish disappears or dies...

Probably disease though.

:lolspin: She does, indeed, hate my hobby. I keep telling her that all the things I do to the tank are for our son, because he loves the fish, and the colors, and movement. Funny thing is, my son is 7 months old. He also loves ceiling fans and floor lamps. :spin2: Joke's on her. We just sold off alot of the equipment for this tank. The new tank is coming on Tuesday! Hahah.

Back to the point, I agree about the inverts living through all of this. The tank now just has a heater and a couple powerheads in it. I sold the light fixture, and sump, and return pump. My hermits are still walking around happily, and I still hear my pistol shrimp snapping from time to time. I was always under the impression that inverts were extremely sensitive to water parameters. Although, to disprove that theory, I had a bucket on my back porch for two months, sealed, in the heat of summer. When I brought the bucket back in, I found two living hermits that I didn't realize were in there.

And you're correct in thinking that there were no external signs of disease.

 

[Dooly]

heres what I think..

2 clowns missing = your cat got them (they either jumped, or your cat went fishing)
mandarin = starved to death
clown nose down in sandbed (internal parasites)

 

[Conesus_Kid]

but if you DON'T have a refugium on an opposite schedule, at night, plant metabolism consumes oxygen, doesn't it? and can cause fluctuations in pH? so if the tank isn't lit 24/7 fluctuations in oxygen and pH are possible, no?

see here, for example:
http://en.wikipedia.org/wiki/Photorespiration

Even if the O2 emission is a net positive, if O2 is consumed at night and oxygen is not produced, wouldn't you risk depleted oxygen and pH fluctuations?

I should know this, I'm actually a plant scientist, but it's been a long time since I had to study or use this...

Fair enough, Lisa. However, I can't imagine that the algae would consume more oxygen that it releases.

I don't believe that hypoxia is the culprit here. If it were large tangs that were croaking or if he didn't have any powerheads in the aquarium, perhaps it might be a possibility.

Looks like we've still got a mystery on our hands!