Why is Water Flow So Important in a Reef Tank?

If you were asked to name some of the differences between a freshwater tank and a reef tank, you would probably list things like salinity and lighting requirements. Another difference you shouldn’t forget to consider is water movement. Water movement is important in any aquarium but it is particularly important in a marine tank, especially one that houses corals. Keep reading to learn more about the importance of water flow in a marine tank and to receive some specific tips for cultivating proper water movement in a coral tank.

Understanding the Basics of Water Flow in Marine Tanks

When it comes to water flow in your marine tank, you need to understand more than just what it is – you need to know why it is important. Not only is water flow an integral part of an authentic marine environment, but it plays an important role in gas exchange. As your fish take in oxygen through their gills, they produce carbon dioxide as a waste product and that carbon dioxide can build in your tank water. When the CO2 levels in your tank get too high, it can have a negative impact on the pH and the alkalinity in your tank which, in turn, could cause problems for your fish.

Another important thing that water flow accomplishes in a marine tank (particularly a reef tank), is sweeping accumulated detritus away from your corals. Live corals have a mucus coating that serves to protect them. When water flow in the tank isn’t strong enough, that mucus coating can become too thick and excess detritus can get stuck in it which may cause your corals to develop an infection – it could also suffocate them completely. Lack of water flow for corals can impact photosynthesis and calcification rates – it can also prevent food from flowing to the corals where they can get it. Corals survive on the plankton and phytoplankton in the water but they won’t get the food they need if the water movement in your tank isn’t strong enough to carry it there.

Before getting into the details of water flow for corals, you should take some time to learn about the different types of water movement that can be used in a marine tank. One of the most common types of water flow in the ocean itself is created by waves and it is known as surge. A surge, or wave, is a periodic rush of water that occurs when the wave passes over the reef – it is a back-and-forth type of movement and it is very beneficial for corals. Another type of water movement is turbulence, the random swirling of water in all directions that occurs as one current collides with another or with a solid object.

In the reef tank, the most common type of water movement is called laminar flow. This simply describes the flow of water in one direction. In the ocean, laminar flow is usually found in the deeper parts of the reef at depths of 50 feet or more. For the most part, the types of coral kept in reef tanks are naturally found in the shallower areas of the reef at depths less than 40 feet. This being the case, the best types of water movement for corals in a reef tank are surge and turbulence. There are a number of different devices and pieces of equipment you can use in your tank to accomplish this goal – you’ll learn more about improving water circulation in your marine tank in the next section.

Tips for Improving Water Circulation in Your Tank

Now that you have a better understanding of why water movement is important in a reef tank and which types of flow are needed, you are ready to learn how to create the ideal water flow in your tank. Here is an overview of some of the devices and equipment you can use:

Powerhead – Not only are powerheads inexpensive but they are one of the simplest types of tank equipment to operate and maintain. The problem with powerheads, however, is that they only produce laminar currents – you also have to be careful about where you point the powerhead. You shouldn’t point it directly at your corals because it could prevent them from opening or might even damage them. To use a powerhead effectively to create flow in your tank, use PVC and various fittings to spread the flow out to create a gentler current.

Oscillating Powerhead – Also known as a power-sweep powerhead, an oscillating powerhead allows you to direct the flow of water over a wider area. The powerhead actually rotates, spreading the flow over a much larger area than a traditional powerhead without the need for PVC attachments. You can place this type of powerhead anywhere in your tank, including behind rocks or other decorations.

Electronic Wavemaker – The best way to use an electronic wavemaker is to pair it with a powerhead or power-sweep. The wavemaker is simply an electronic device that turns the powerheads on and off at random intervals to mimic the wave-like effect of surge flow. These devices can get a little expensive but it is a worthwhile investment because the better wavemaker models offer a “soft start” feature which doesn’t just shut the powerheads on and off, it tapers the flow down and up to mimic the gradual surge and flow of water in your reef tank.
Dump Bucket – This method for creating flow involves dumping water from one container to another to create water movement. The main problem with this method is that it creates a lot of air bubbles which can irritate your corals – they can also disrupt your viewing of the tank. Dump buckets also tend to produce a lot of salt spray which can accumulate on your tank lighting and lead to degradation over time. It is also more difficult to control the flow created by a dump bucket than by a powerhead or wavemaker.

As you take steps to improve the water flow in your reef tank, there are certain things you should be on the lookout for. For example, water flow is one of those things where more is not always better – too much flow could prevent your corals from opening and might make it more difficult for them to feed. You should also be wary of increases in tank temperature driven by the heat produced by your tank equipment, especially powerheads. Be mindful of salt spray that can accumulate on your lighting and make sure that your electrical outlets are grounded and safe to use. Be sure to follow any instructions that come with your tank equipment and don’t forget to create a drip loop with your power cords.

Cultivating and maintaining a thriving reef tank can be a challenge because there are many specific requirements that must be met. Not only do you need to keep the salinity and the water chemistry in your tank within the proper ranges, but you also have to think about the water movement in your tank. Inadequate water flow could cause your corals to suffocate and die so make sure you have the right equipment in place to create the degree of flow your corals need to survive.