Specific gravity is the measure of relative salinity or the amount of dissolved salts in your aquarium water in comparison to pure water. Being reef aquarists you all be aware of the importance of maintain a constant specific gravity in order not to stress the inhabitants of your aquarium. Measuring specific gravity on a regular basis is essential to keep up the idyllic environment for your aquatic inhabitants. It is important that you never ignore this fact even if sometimes you might think it is not as important compared to the other factors that need to be taken care of in a reef tank.