Dave,
You know another thought I had is the seahorse mounted on the frogfish and the one on the substrate might actually be there on purpose? Maybe to feed on a few bits stirred up when the frogfish feeds?
I just kinda doubt they don't sense the frogfish there, especially the one perched on him -- but I don't know??? Still "Russian Roulette" a bit for sure!
Thanks, Carol
He, he... in my 'spare' time I'm doing my PhD on seahorses, in particularly Hippocampus whitei (the seahorse in the pics) and one of the things I'm looking at is what predates on seahorses.
Pretty close to the top of that list is Anglerfish!! I often find the anglerfish hanging around the seahorses and on two occasions I've now seen them munch a seahorse! So they are not very friendly towards them thats for sure!
I think on this occasion both seahorses in the image were ignornant of the anglerfish as he didn't move the whole time I was watching and he was pretty well camouflaged against his orange sponge. Interestingly enough, only 6 weeks ago this anglerfish was yellow in colour and about half the size. I've been watching him gradually change his colour to match his sponge habitat and he's growing quickly... probably because there are lots of seahorses about! 
You do make me chuckle though... resisted the SLR for so long and now BAM! you are on your second one..
Not only am I on my 2nd one, I kept my D80 so I can take 2 camera's around with me on dives!!! 
But I do still 'occasionally' miss my CP5000 for macro shots!!!