here's the situation. on saturday afternoon i bought an anemone along with a false percula clown, a yellow boxfish, and a starfish. i came home, dropped all of them into my 45g tank. the existing fish are a yellow tang, two blue damsels, and a striped damsel. that same nite i did a 50% water change. i know it was a bad idea but i really had to do it. after the water change everything was fine, the water was a little cold so all the fish were in a little state of shock. i left the light and heater on all nite to warm up the water. the next morning (sunday) i woke up and everything seemed quite well. all the fish were swimming and the percula was playing with the anemone. well on sunday nite, i turned off the light at nite and woke up on monday morning and turned the light back on. i fed flake food and everything was still fine. i turned the light off again after a few minutes and left for work. i came home that evening and the anemone was floating at the top of the tank and now the percula clown is just swimming around the same place where the anemone used to reside. what could have caused the anemone to die?