Reef Aquariums | Water Movement in Reef Aquariums

Water Movement in Reef Aquariums


Filed Under reef aquariums, water movement |

Welcome back. We just finished the series on filtration on the reef aquarium and will now touch on the topic of water movement. A reef aquarium is a small, simulated section of the ocean. Most of the organisms living in the aquaria will be accustomed to large water movement due, in part, to wave motion and tidal motion in the ocean. These organisms, typically sessile creatures such as corals, clams, etc,  have come to rely on the currents to bring them food, oxygen, other nutrients, and equally important, to remove waste products. Therefore, it is essential for growth and well being of the organisms to simulate that motion to the best of our ability.

Given that the aquarium is nothing more than a sealed box, we are somewhat limited by what we can do to create water motion. Typically aquarists will use a combination of submersible pumps, powerheads, external pumps, and other such devices to circulate the water in their aquarium.

Submersible and external pumps are often placed either in the sump beneath the aquarium as the return path, or on a closed loop path through which the water flows.  The return line from the sump, while capable of creating water motion with carefully aimed exhaust streams, is secondary to water motion and primarily used as part of the sump system. Additionally, submersible pumps in the sump will introduce some degree of heat into the system. On the other hand, closed loops are purely dedicated to moving water around the aquarium.

To create a closed loop, aquarists often drill several holes in the back of their aquarium through which bulkheads are attached. The input to an external pump is connected to one of the holes, and the output of the pump is connected to the other holes. This creates a specifically plumbed loop for water to flow through. As water returns to the aquarium from the pump, the water is aimed in the direction desired using flow manipulation devices. Closed loops are a powerful way of moving water around a reef aquarium without introducing any heat from the pump to the water column.

Powerheads are a more common method of moving water around the aquarium. They are placed directly into the aquarium, and yes, they will introduce heat as well. Powerheads can be readily aimed wherever the current is desired. They come in various sizes and powers ranging from small pumps geared towards nano aquariums, to larger pumps designed to move large swaths of water across the tank. For Tank 1.0, 4 MaxiJet 600s were chosen to move water around the aquarium. These were then replaced with MaxiJet 1200s when the wavemaker was introduced, see below.

The placing of the waterheads is as important a choice as the type. Depending on the types of corals, and other organisms, in the aquarium, the goal of water movement ranges from using a gentle flow to eliminate dead spots in the tank in which detritus can collect to turning over the water volume of the tank 30-50x per hour. The general rule of thumb for most reef aquarium is at least a 10x turnover with minimal dead spots. This means that for a 50 gallon aquarium, the water movement should be a dedicated 500gph worth of closed loops and/or powerheads in the aquarium.

Equally important is the randomness of the water. The ocean is does not constantly flow from left to right, similarly the aquarium should not constantly flow in one direction. The powerheads should be arranged to create as much chaotic water motion as possible. Devices known as wavemakers can be employed to help introduce randomness into the system. These devices come in mechanical and electronic versions. The mechanical versions, such as the SCWD, have gears and impellers in them and periodically shift flow of water from one port to another. SCWDs typically cost upwards of $35.

The electronic wavemakers, such as the Red Sea WaveMaster Pro, control power going into the pumps and turn them on/off as needed in a random fashion. The WaveMaster sells for around $150 and was chosen for Tank 1.0. One thing to keep in mind is that a wavemaker will run not run the pumps all of the time. This means that the maximum rated waterflow of the pump is not what you will be acheiving as the device turns pumps on and off. On Tank 1.0, the original Maxijet 600s which were selected were traded in for MJ12s once we realized that at any given time only 2 of them would be on. This allowed us to maintain at least 590gph of water movement at all times.

That concludes the post at this time, we hope that you will come back to join us and learn about our reef aquariums.

Comments

Leave a Reply