Generally speaking, you should check pH and water levels in your tank daily. If you have a saltwater tank, its also important to maintain proper salinity. Tips for Changing Fish Tank Water.
Managing Salinity. The fundamental difference between freshwater and marine aquariums is their respective salt content. The salt level is usually reported as either salinity (parts per thousand [ppT] of salt in water) or specific gravity (the density of the solution relative to fresh water).

As we can see from the illustration, Managing Salinity Levels During Saltwater Aquarium Water Changes has many fascinating aspects to explore.
After a few water changes, your salinity should be back to your desired level and then you can resume your normal routine. In Short. Salinity swings are a common part of marine aquarium ownership.

Do you know what the water parameters for your home aquarium are? For both freshwater and saltwater (marine) aquariums, read on to find out what LiveAquaria recommends for each.

Furthermore, visual representations like the one above help us fully grasp the concept of Managing Salinity Levels During Saltwater Aquarium Water Changes.
Small Saltwater Aquariums (less than 40 gallons) Start with two equal sized containersthe Seachem Just Add Water 5 Gallon Water Jug TWO PACK work well , and fill one with RO/DI water. The second jug will be used to collect the water removed from the aquarium.
The salinity of saltwater aquarium water isnt a scary, unpredictable monster. Its a simple, logical parameter that, once you understand it, becomes second nature.