Water Motion/Tank Circulation

Power heads in your reef aquarium are the most common way that hobbyists create the water circulation in their tanks. Power heads (pictured at left) are small water pumps that sit inside of the tank and typically hang on the wall and circulate water within your aquarium. Water circulation is very important in your aquarium and power heads are probably the cheapest and easiest way to provide good circulation in smaller tanks of say 75 gallon and less.

Power heads are great because they're small, inexpensive, and they can be placed in various locations throughout the tank to provide circulation evenly. In your tank don't make the mistake that many beginners do by placing them only at the surface of the water. Some power heads need to be about halfway down the tank wall in order to provide circulation to much lower parts of the tank.

Natural Ocean Flow

Ocean circulation occurs in all directions and in varying intensity, so you don't only want to create circulation at the surface or in one direction.

Advantages of Good Flow

Circulation at the surface IS important for oxygen exchange and to keep the amount of oxygen in your water saturated. However just because you see a lot of turbulence or movement at the surface of the aquarium doesn't mean that you're getting good circulation within the tank itself. So it's very important that you place Power heads at different levels within the tank to provide circulation. Not only to corals, but also to the live rock to keep that oxygenated and to allow the microorganisms that need oxygen to survive.

It's also a great idea to place a least one or more of your power heads on one of the inexpensive automatic timers. You can buy them from your local home improvement store. These timers typically cost less than $10 and can be used to turn your power head on and off on a regular basis. The advantage to this is that rather than getting the same current throughout your system all the time, if one power head shuts off than it will change the pattern of all of the currents within the system. In some areas you may get additional current or water flow to them, which is important.

Random (non laminar) Flow is Best

Random variable water flow that varys in direction and intensity is beneficial to your tank. You want to avoid flow that is laminar ( in straight lines) as much as possible. And you want to try to provide as much a randomness as possible. When you are setting up your power heads handed timers for your power heads. Keep in mind, you can put each power head on a different timer or you can put one of your power heads on one timer and leave the other power head on continuously. These settings will not produce constant laminar flow, which is much healthier for your corals.