What Is Flow?

Flow is simply the amount of water cycling around in your aquarium. This isn’t to be confused with turnover. Turnover is number of times the water in your aquarium is cycled from your display tank to your sump and back again. Your return pump is what handles turnover. Powerheads or circulation pumps are responsible for flow. Your return pump does create flow but you’ll need more to get the amount of flow you need. Flow in your aquarium should be 20x to 40x the volume of your display tank. 40x if you have SPS corals and 20x for LPS and softies.

Why Does Your Tank Need Flow?

Flow is essential for getting water into your live rock. Live Rock is where the good bacteria in your aquarium lives. The good bacteria breaks down the waste produced by your fish and uneaten food. Ammonia breaks down into nitrite. That is then broken down into nitrate. Nitrate is broken down into nitrogen gas which bubbles out of your aquarium harmlessly. Higher flow is necessary for the health of SPS corals. LPS and softies need lower flow for their more delicate structures.

What’s The Best Kind of Flow?

Constant flow is typically sufficient but it’s not ideal. A strong current continuously blasting away at your corals can stress them out, cause damage, or even kill them. Varied flow is best because it gives your corals a break. It’s also good because it helps stir up waste so that it can be cycled through to the sump. Good varied flow will also help dislodge debris that can get caught in corals. This is how a real reef works. The closer we can get our tanks to a true reef environment the happier our fish and corals will be.

How Powerheads Create Varied Flow

Wave makers are basically just controllers that are programmed to vary the output of your powerheads. The simplest of wave makers just turn your pumps on and off in a pulsing fashion. This will get the job done but can be hard on the powerheads and shorten their lifespan. The better wave maker systems can ramp up and down the volume of flow. This avoids the harsh and abrupt on/off cycling of your powerheads. The best aquarium wave maker is one of this type. It also can be programmed to create a wide variety of flow patterns.

Wave makers can be programmed to make an actual wave in your tank but that’s more for show than anything. Varied flow with turbulence produced by intersecting flow patterns from multiple powerheads is ideal. A great varied flow pattern would be to aim 2 powerheads at each other and ramp one up while ramping the other one down. Once one reaches 100% the other should be at 0%. Then reverse the process. This causes the turbulence intersection to pan back and forth across the aquarium. This way all parts of the tank should get very good flow.

AC versus DC Powerheads

AC powerheads run on standard current from a wall outlet and require no power brick to convert the power. They are technically more efficient because of this but they are not able to be adjusted in speed. When on they run at 100% of their capacity. They can be used for wave making but they have to be toggled on and off to do so. This process of frequently turning on and off of the powerhead can be quite harsh and shorten the life of the powerhead. It’s suggested that you try to purchase a more robust quality powerhead and try to use longer wave cycles to cut down on wear and tear.

DC powerheads require a power brick to convert the AC power to DC. These powerheads can be adjusted from 0% to 100% of their capacity and usually come packaged with a controller. The controllers vary widely in their abilities from manufacturer to manufacturer. The better controllers allow you to control multiple powerheads and create all the wave patterns that you would need.

Third party controllers can also provide features and flexibility that the manufacturers controller can’t. Reef controllers are usually the most ideal solution since they can be used to sync wave making with other equipment and parameters of your aquarium. They also usually have very good reporting features that can alert you to issues.