Most reef tank owners are aware that keeping their corals within the right temperature range is critical to keeping them healthy and developing. The which most corals require for living, will die or evacuate the polyps if the temperature is too low or too high. When algae leave the coral, the white base calcium carbonate of the coral is exposed, which is known as coral bleaching. You might recall hearing about in parts of the world's coral reefs, which started in the early 1990s.
According to the National Oceanic and Atmospheric Administration, coral thrives best at temperatures between 73 and 84 degrees Fahrenheit. So, to begin, it's usually advisable to maintain your aquarium within this range.
What is the optimal temperature for your reef tank, given the vast temperature range in which coral may thrive? Looking at the temps when your corals were in the wild may be the best method to make a decision. You can observe where corals grow in the wild by looking at Coral Reef Regions Around the World. When you compare this to the temperatures listed in NOAA's Sea Surface Temps, you'll notice that the great majority of coral reefs are situated where water temperatures range from 80 to 89 degrees Fahrenheit, with some even reaching the lower 90s in the Red Sea.
The Indo-Pacific, Caribbean, and Red Sea are the primary sources of coral for the aquarium sector. Asking where your corals were sent from when you buy them is probably the easiest method to find out.
Because most aquarium corals are gathered in the Indo-Pacific and Caribbean, where are typically between 85 and 89 degrees Fahrenheit, you may not need to be concerned as long as your tank temperatures do not exceed or fall considerably below these ranges.
However, in saltwater aquariums, greater water temps might cause some major difficulties. The lower the (DO) in saltwater (and freshwater) gets, the worse it is for all of the species in your tank. In general, levels in seawater are roughly 20% lower than in freshwater.
Let's simply assume that seawater near the equator, where surface water temps are in the mid to upper 80s, stores roughly two-thirds as much DO as water at the poles, where the water is extremely cold, without getting into all of the scientific calculations, formulae, and statistics.
DO levels are vary for different fish species. The Clownfish, for example, requires roughly 7 mg/l of dissolved oxygen, whereas the Marlin requires about 3 mg/l. Surprisingly, most saltwater aquarium animals require greater amounts of DO than most other fish in the ocean. Most saltwater tropical fish are found on or near reefs in the wild, rather than in the deeper ocean waters, where the DO is greater due to waves crashing on the reef aerating the surface water.
Higher water temperatures also hasten the decomposition of materials in saltwater. Bacteria increases its rate of reproduction, which increases O2 consumption and reduces the DO level in the water.
Most of the saltwater tropical fish and invertebrates in our marine aquariums come from natural waters with temperatures averaging in the low to mid 80s, so this would be an appropriate goal temperature for our tanks.