by Saltwater Smarts | Feb 29, 2016 | Fish, Invertebrates, Reef, ScienceWhen you realize the salinity in your aquarium is off, making slow adjustments is importantSaltwater Smarts visitor Andrew had the following question about our post titled “5 Tips for Maintaining Stable Salinity in a Saltwater Tank.” Since we get similar questions quite frequently, we thought it might be helpful to elaborate on our response in today’s post: QuestionThis article says, when doing a water change, make sure the salinity is the same as [that of] the dirty water. My question is, what if the salinity in the tank is a little high or low?” – Submitted by Andrew Answer If the salinity (hereafter expressed as specific gravity) in your tank is slightly off, you can adjust it up or down in a variety of ways. Let’s look at each scenario separately, keeping in mind that each remedy may need to be repeated several times to restore the desired level: If you need to raise your specific gravity, your options are to: Dissolve a small amount of sea salt in aquarium water (e.g., in a cup or beaker) and drip the mixture slowly into your sump or a high-flow area of the tank. This is best done in several doses over the course of a few hours or even a day or more, depending on how far the level must be raised. When performing water changes, replace the dirty water that you remove with clean salt water mixed to a slightly higher-than-normal specific gravity. Top off water lost to evaporation with salt water rather than fresh water until the desired specific gravity is reached. If you need to lower your specific gravity: Remove small amounts of salt water and replace them with equal volumes of purified fresh water. During water changes, mix your replacement water to a slightly lower-than-normal specific gravity.