I had a power head. I had actually three power heads in different parts of the tank, one was used specifically for surface agitation.
Power heads below the surface usually don't cut it with a good macro bomb, which is why I specifically mentioned things like a bubbler or elevated output (and a vigorous one at that - just a dribble won't cut it either). In other words, if you had a miniature oil spill on the surface of the water, would it just get pushed around as a continuous surface, or would something actively break it up? The common case for marine tanks is that it would just get pushed around, even when powerheads are rippling the surface quite a lot. So, if a film gets there...it's bad news. In my many, many, many iterations of having macro bleedouts, mass dieoffs, and stuff going sexual over the years, there are exactly two things I have had that made macro bombs into non events: bubbles popping and fast jets of water that are disconnected from the surface by quite a bit. Macro goop going into the water seems to really inhibit gas exchange by forming films early on. pH drops off fast and fish start gasping within minutes sometimes. The films can be really hard to see, but I was able to see it on some tanks quite a few years back when I first started keeping macro, which is why I started putting a bit of airline into all tanks that have macro. For me it made the difference between gasping fish within minutes and total non-events. I haven't even needed to do WCs the last few times I've woken up to opaque green tanks (most recently in my 55gal).
Of course, this assumes you are certain the macro bomb caused the deaths and not something else in the tank that happened to have a low-probability timing (e.g. hidden nudi nuke), although it is pretty classic macro-bomb-sounding.
No, I don't have a nudi that I'm aware of in that tank. It was a macro bomb I'm pretty sure. I just wasn't home to prevent it like I normally am. I know about the film and can usually adjust a powerhead and remove offending Halimeda when I see it, or do a small water change, which breaks up the surface film too. I just wasn't home and my family didn't know what to do. They said the tank was fine in the morning, by the afternoon, everything was dead. Not a slow developing thing, but very sudden. I assure you, there was enough ripple in the surface normally. I'm really careful about that. It breaks the water quite a bit and prevents the film. What may have happened and I noticed this is that that particular power head was rather clogged, again, probably because I wasn't there as much to monitor what was going on.
Now, I do feel bad. You made me feel really bad, Donya!
Just teasing. You're absolutely right and it's something I have to keep on top of if I decide to keep macros again. If I do macro again, I'll be adding, as I really hate bubbles, sorry, probably an HOB with a strong jet to break up the water surface further.
What stinks is that I knew this (I did my macro research, you all know this) and was working to prevent it, and it still happened. This is the problem with having multiple reefs and being a performer. I have one busy performance weekend and something goes to pot. All it takes is for a little thing to become clogged that wasn't clogged before...
Can somebody give me a darn hug please...
Lissette