Thank you everyone for the informative answers. I appreciate it
One of my zoa colonies mysteriously stopped opening for two days. All my other corals (a few softies, lps, and more zoas/palys) seemed perfectly normal so I was kind of stumped as to why this could be. My parameters as far as the "big three numbers" are all at 0. I don't have a test kit for calcium but I think I might just invest in one instead of guesstimating in the future. The tank is under 30 watts of 50/50 compact flourescents at the moment but I've ordered a 72 watt t5 fixture which should arrive within the next two weeks as I know the current lighting is pretty ghetto. Anyway so I tried googling possible reasons for zoas not opening as well as potential solutions, and dosing vitamin C popped up a few times. This is where the idea came from. I checked my medicine cabinet at home and saw that I had Vitamin C and Calcium by Jamieson's. I read in a few places of people using drugstore vitamins in their tanks, but felt unsure about it so I thought hey I'll just ask the canreef crew lol
After reading some of the replies to this thread, I did not add either supplement to my tank. I did however move the zoas to my extra 5 gallon tank under 40 watt t5's. Strangely enough they opened up almost right away. I have three guesses as to why this could be: 1) They need more light 2) There was some little pest irritating them which maybe got shook off during the transfer between tanks 3) They're weird