Can you have too much flow in a saltwater tank?
Flow is an important part of being successful in marine fish keeping so it is important to strike the right balance. You don’t want too much flow and similarly, you don’t want too little.
Water movement is primarily achieved through the addition of powerheads and wavemakers. Good movement promotes gaseous exchange in your saltwater aquariums water meaning that it provides increased oxygen levels and therefore decreased carbon dioxide.
A good water current also evens out fluctuations in temperature. In warmer climates, wave makers and gyres in reef tanks will constantly be moving water around allowing warmer water at the top of the water column to mix with the cooler water below, creating a more even and consistent temperature.
Good water movement stops detritus from settling and helps it eventually find it’s way into the filtration system.
Signs that your flow might be too high
Flow rates are usually given as a general guide but here are a few ways to tell if your flow is too high:
Sand blowing up into the water column
Fish hiding or at worst, not surviving
Coral polyps not extending or coral not growing
High flow and fish:
Saltwater fish need good water movement in order to help keep them healthy and active. A fish with a healthy immune system is not only one that is less prone to disease and stress but also more able to fight them off if they do happen to catch them.
Like us, fish need exercise. Too weak a current will make fish lethargic, too strong and they will keep hiding to avoid the force.
The strength of flow needed also varies depending on what fish you have. Fish such as Batfish and Lionfish cannot handle strong currents.
It’s also good to remember that higher oxygen levels are not only needed by the fish but also invertebrates.
High flow and coral:
Good water movement brings nutrients and food to the coral and takes away their waste and by-products. This, amongst other things, results in healthier, faster growing coral.
Not only this but it allows for even temperatures in the water column. If the water were to remain too hot in one specific area near coral, it could result in coral bleaching due to stress.
Different coral types however do better in different types of low. In general:
Soft coral prefer areas with low water movement. Soft coral examples are Ricordea, Zoa, Clove Polyp, Mushrooms. (You can see our guide on soft coral for beginners here.)
SPS (Soft Polyp Stony) coral prefer higher flow but will retract if being hit too hard. Examples of SPS coral are Montipora, Acropora, Stylophora, Leptoseris.
LPS (Large Polyp Stony) coral prefer a moderate current, however not directly. Examples of LPS coral are Favia, Goniopora, Acans, Frogspawn.
If coral are encrusting and you see good polyp extension, that’s always a good sign. It means they’re doing well!
Remember that powerheads should never point directly at coral but should provide water movement around it.
How to work out flow rate for a saltwater aquarium
Please see this article where I explain more about water flow and turnover rates along with how to work these out.
So yes, there is such a thing as too much flow in a saltwater tank. It may take a bit of tweaking initially but if your fish and coral look healthy, you should have reached that happy medium.