Oxygen is one of the most important aspects of aquarium management, since without adequate dissolved oxygen in the water the fish will die. Test kits can provide a way to monitor oxygen levels, but in most cases good management will ensure that there is plenty. If oxygen levels fall too low in a saltwater aquarium there are some easy ways to give it a boost and make life better for the inhabitants.
Most filtration systems for saltwater tanks keep the surface of the tank agitated, providing for an adequate exchange of oxygen. If you use a type of filtration system that doesn’t stir up the surface of the water, consider replacing it with one that does. The water movement doesn’t need to be extreme to promote the exchange of oxygen. The main goal is to ensure that the surface tension is broken to allow a more efficient oxygen exchange.
An air pump with an air stone attached is an excellent way to add oxygen to an aquarium. For permanent installation a very fine air stone sits near the bottom of the tank, emitting a steady stream of small bubbles that move slowly up to the surface. This has the double effect of breaking the surface tension as well as carrying unwanted gases out of the water. To add oxygen in an emergency, place the air stone near the surface of the water instead of at the bottom to avoid stirring up debris.
Living plants remove carbon dioxide, use waste products and add oxygen to a saltwater aquarium. The more plants the aquarium has, the more the oxygen benefit, though it’s best not to overcrowd the tank. Good choices for a marine environment are plants, such as the Halimeda, Maiden’s Hair and the Shaving Brush plant, but any plants will help. Limit air stone use around plants, since the bubbles can affect the carbon dioxide levels and interfere with the plants’ ability to thrive.
Many different factors can impact water’s ability to hold oxygen. Temperature and salinity are two important considerations. Cold water is able to maintain higher oxygen levels than warm water, so keeping the tank on the cooler side of the acceptable range helps with oxygen. The same is true of salt, since the higher the salinity of the water, the less oxygen it can hold. Other ways to increase oxygen levels are to remove excess fish, since too many fish will decrease oxygen significantly, and to keep the tank clean. Decaying matter uses up oxygen and reduces what’s available to the fish.