Temperature is debatable in our hobby. Yours is very low however. Temperature stability is very important. My opinion is 77 degrees. Many like to keep their tanks warmer, 80 degree range, metal halide lighting and Texas summers make this the norm. The argument is that many area's along the equator have 80 degree temps and many Corals metabolism is increased, thereby they grow quicker at higher temps. Delbeek, Sprung, and Paletta recommend 75 - 77 degrees in our closed systems.