AskBRS Tips For Perfect Flow
Water flow in a saltwater aquarium is significant for a few reasons. First and foremost, the water flow through your filtration system generated by the return pump allows the life support equipment (filtration) to clean and oxygenate the water. Internal flow that is generated by powerheads and wavemakers helps keep waste suspended in the water column, promotes healthy gas exchange, delivers food and nutrients to the fish & corals, and aids the corals in a variety of biological processes including the ability to expel waste material. Without adequate flow, the health of both your fish and corals would suffer tremendously. Modern aquarists pay careful attention to how much flow is generated, the flow patterns, and how that flow interacts with the aquarium inhabitants.
We've distilled down our top 5 tips to help you master flow by answering some of the most frequently asked questions from our AskBRS Facebook Group.
AskBRS is an online saltwater aquarium community where you can interact with over 80,000 hobbyists to talk tank, ask questions, and stay connected.
1. Choose The Right Pump The First Time
Like most things, it's better to buy something reliable the first time than to find yourself needing a replacement only a short time down the road. This not only applies to the quality of your aquarium pumps and powerheads but also when it comes to the size and power of your pumps. You want something well-built and reliable and most importantly, that can deliver the flow your aquarium requires.
Purchase a pump that is too small, you will end up buying a stronger pump quite soon to accommodate your tank. Should you find yourself with a broken pump and a tank without flow, your fish and corals' lives are immediately threatened.
Did you know fish can die inside of an hour without flowing water that is properly oxygenated?
The point is to budget accordingly for a reliable, high-quality return pump and powerheads. You will end up spending more in the long run should you try to cut corners when it comes to pumps. Not sure which pump is right for you?
2. Not All Flow Is Created Equal
When shopping for powerheads and/or wavemakers to create internal flow in a reef tank, it is important to understand the various flow patterns that different powerheads create. The two most common types of powerheads are the propeller pumps and gyre pumps.
Gyre pumps have a thin profile and are very versatile - they can be mounted close to the water's surface or even vertically. They excel at creating flat sheets of laminar flow that ultimately create a circular "gyre" flow pattern around your aquascape.
Propeller pumps are akin to a boat prop inside a protective cage and come in a wide variety of designs that produce varying degrees of wide to narrow-angle turbulent flow.
3. Pump Placement Can Make All The Difference
With the previous knowledge in mind, the placement of your powerheads can make all the difference in terms of moving every drop of water in your display. The goal of your powerheads is to eliminate "dead zones" which are problematic areas of your display aquarium where there is little to no flow. These "dead zones" are typically down in the bottom half of the aquarium, inside and around your aquascape. The reef rock deflects water flow and since both your pumps and rocks are stationary, it can be difficult to get flow in every nook and cranny.
Most reef tanks over 25 gallons will require at least x2 powerheads to get flow where you need it. Based on your particular aquascape and pump types, there are several different configurations you might consider. The idea is to find the best balance where the pumps are moving water throughout as much of the tank as possible without creating an eyesore - you wouldn't, for example, mount your powerheads directly on the front viewing panel of your tank.
4. When It Looks Like You Have Enough, Add More
Looks can be deceiving when it comes to flow and for the most part, corals and fish can handle much more flow than you might think. Inside our tanks, the water is trapped inside four glass walls which means it's being deflected and constantly diffused by your aquascape. If your fish appear to always be swimming against currents and your corals are undulating constantly, you are getting close to the ideal flow in a typical reef tank.
When choosing powerheads and return pumps, it's important to always veer on the side of more flow is better. Modern DC pumps and powerheads are controllable which means you can control the speed of the pump, and therefore, the velocity of the flow. You can always slow down the flow to accommodate your tank but you cannot make a pump go faster than its maximum speed. Having a little extra pump power is never really a bad thing. This also allows you to crank up the flow down the road as your tank matures which is a pretty common practice thanks to growing corals.
5. Lighting & Flow Go Hand In Hand
If you have corals or plan to keep corals in the future, you probably have learned that different corals have different preferences for lighting and flow. For the most part, the more light a coral gets the more flow it demands to maintain healthy biological processes.
For example, SPS corals are high light-demanding corals and when you set up an aquarium for SPS corals, you will want to choose and place your powerheads to accommodate very strong flow patterns. LPS and soft corals generally thrive under medium to low light conditions and, therefore, require less intense flow. A great analogy would be like exercise and the human metabolism where flow is like exercise for the coral.
The most advanced coral growers that are pushing the boundaries with high light output in an attempt to achieve more robust coral growth are increasing the water flow in direct proportion to the increase in light output.