That's kind of where I was going with it - as a *possibility*. If there's no voltage (did you check with the heater actively heating?), fish get a varied diet with lots of greens and water quality is good, then it can possibly be ruled out and look to other possibilities such as a crab/mantis or whatnot. It's just unusual for one of the larger fish in the tank to come down with shreds if there's a hidden predator.
The missing clown *could* be chalked up to a predator, and I've only seen one or two instances of HLLE in clowns (horrid water quality over a LONG time frame) but usually they don't show signs of it at all but tangs and angels come down with it first.
A picture would be very helpful - I've learned to recognize the differences between mechanical injury and erosion - sometimes it can be really obvious if one knows what one is looking for, but sometimes it's pretty subtle - especially in the beginning stages of it.
Most mechanical injuries will heal completely if there's no secondary infection. Early HLLE can be reversed if the cause(s) are corrected quickly before the scarring becomes too severe.
In the case of my "rescue" fishes, they were exposed to various ills for long periods of time, and the progression was beyond complete reversal by the time we got to them. At this time they are free of the condition but they are permanently disfigured.
Jenn
