Sherlock Holmes anyone ?

[MalHavoc]

If some macro had gone sexual, you would have noticed it in a big way, since it's usually accompanied by your tank water getting quite cloudy. How deep did you siphon your sand bed? Siphoning a working DSB is usually a 'bad thing' because it can disturb the stratification that occurs and can kill off some of the bacteria that live deeper down, resulting in a lowered ability to process nutrient.

I'd try to find that cuke. All cukes are toxic to some degree. The less brighly coloured ones seem less toxic, but DGenR8, a mod over on RC, attributes a mysterious tank crash that wiped out all his fish a few years ago, to a missing black cucumber. Something to think about.

It's possible that the LTA poisoned your fish. Anemones that are dying in a can do terrible things to a reef tank. I know you said that it looks fine, but I'd watch it very carefully over the next day or so. Perhaps do a water change as well. If it looks fine, though, it's probably not what caused stuff.

Have you measured your ORP? I'd be interested in knowing if it dropped over the last 24 hours or so. That may be an indicator of something going awry.

Sorry to hear about the loss