Low temps can be great for reef tanks!!!

Finally got the tanks temp down to 21c/22c, all are looking very happy!
Corals are glowing, fish are more relaxed due to low metabolisms, oxygen levels are at the max, ammonia production is reduced resulting in more stable PH and Kh when temps are low, not cold, just low!
18c down to 16c many fish are dieing if your tank has robust parasite numbers, 18c to 20c many can handle that range, in fact many fish and corals from aus water winter temps, where many come from, hits this mark, then 21c to 24c, most all none cold water common aquarium life can handle this range, in fact if stress levels are low in your aquarium, they grow 2 to 10 times slower and attain far better coloration and are much mellower.
There are other sps, lps and algae thriving in the tanks, but these guy are examples of how happy they are with these temps.