In regards to the heater, I would aim for 78F. A heater is one of the most important things in a tank. I would suggest getting a very reliable one. I cannot recommend any as I have never had a nano before. That being said, I have kept N. wennerae, G. chiragra, and S. rugosa at 75F without issue. Can't say it is optimum though. Make sure those zoas are glued down or anchored. My peacock stole one and put it on top of her burrow last week.