Do fish get aneurisms?

[asylumdown]

I lost my copper band butterfly this morning. Has anyone ever experienced a fish with a gill aneurism? When my tank started falling apart in February, my blue throat trigger got a bad case of popeye, and my copper band developed what I thought was a tumour under it's gill flap. I figured both were related to whatever was going on with my water that was killing all my coral.

Over time, the tumour in the CBB's gill grew so large that the gill flap couldn't close completely as it 'breathed', and went from a silvery colour to dark, blood red. For a while it was even protruding out of the gill, but it seemed to grow and shrink at random. The fish's behaviour never changed and it seemed otherwise healthy and I couldn't find anything on it online anywhere so I just left it.

When I fed them before lights out last night, the CBB was totally normal, aggressively chased food everywhere, ate it's fill, etc. When I went to bed I could see him in the dark doing the same post dusk hunt he's done every night for the past 19 months.

Found him dead at 7 this morning. When I examined him, the only thing out of sorts was that thing I thought was tumour. It looked all deflated and wasn't red anymore, kind of like a popped balloon.

Am I rational in thinking this was a burst aneurism catastrophic enough to kill him? Everyone else is out and accounted for, and other than highish nitrates (5ppm), there's nothing obviously wrong with my water. There's no visible disease in tank, and the corals are finally growing like gang-busters again.

[Bowen]

I'm not a reef expert by any stretch of the imagination, but most of my university schooling focused on multispecies physiology. If the aneurism (or whatever the growth happened to be) was connected to a major blood vessel, its rupture could very well lead to the fish bleeding to death just as if it were stabbed in the same place. Given that it was so close to the gill tissue, which has a TON of blood flowing through it, there's a decent chance it was associated with a major blood vessel.

As for behaviour, if the growth wasn't pressing against anything, it wouldn't be causing much (if any) pain. The change in size could be related to a lot of things, but one option that comes to mind is a recent change in activity; racing around for a bit will increase blood flow to the gills, and that could force more blood into the growth.

If you still have the fish, try examining the growth under a bright light to see if there is a tear in it. If it burst from pressure, it will probably be a tear rather than a hole, like a balloon that's been stabbed with a pin.