My serpent star usually sticks a leg out between rocks...i will try and get a piece of squid, clam or whatever to a close proximity of the leg..he will usually grab it and chow it out.
Bacterial blooms can be caused by any number of things. Most often it is a newer tank, semi-established bio filter, tons of nutrients, lighting and off it goes. A recurring bloom (if that was your problem), could also be caused by numerous things. More then likely it was created by excessive food/decaying, and the subsequent amonia spike. A major die-off of livestock could also cause it as well. But I would tend to believe the sudden input of too much food (which decays rather quickly) could have been the cause.
But then, I could be so far out in left field...you just never know for sure after the fact.