Thanks Chasmodes. I had never thought of aiptasias as dangerous to fish. So, when I moved my live rocks into QT, it was to keep the life on them alive, while the display was in hypo. I knew there were aiptasias, but I didn't know of a danger from them. Even when I googled it, I found very little info on their possible danger to fish. And, of course, I don't know for sure that they were the culprit.
I've had a few pop up in the display too. I tried the hot water trick without success. So I decided to try ammonia, since I was already dosing it in small amounts, for the plants. It seems to be working, but I would not recommend anyone else use ammonia, because of the danger of ammonia poisoning. I'm only able to get away with it because of my large tank volume and large plant bio mass. Seagrasses, and most plants, prefer ammonia as their nitrogen source, but in the confines of aquariums it's dangerous, so nitrate is a safer nitrogen source. The best, safest way to give plants ammonia, is to keep a high number of fish. They give off small 'doses' continuously and much more safely.
So there's another big difference between planted tanks and reefs. A high fish load in a reef tank, puts a strain on the system. In a planted tank, a high fish load actually benefits the system.