One of the first things you need to consider when you are choosing your saltwater aquarium is the design of your flow. You may be thinking, “What does it matter. I can just add flow if it becomes an issue.”
I understand the desire to wait and see what the needs of your tank might be in the moment but a successful aquarist makes sure they are doing their research so they are not wasting time, money, or putting the lives of their fish at risk.
Don’t start dropping creatures into your saltwater aquarium without providing a flow rate that will allow your fish to thrive.
Types of flow in reef aquariums
Flow in your Reef tank goes beyond simply how quickly the water is turning over. It also takes into account the design of the flow. There are several common types of flow like Laminar, Gyre, and Turbulent flow. Each type of flow attempts to move the water in a different way for different nutritional distribution and water movement. Take a look at the breakdown of the different types of flow below.
Laminar (or constant flow)
The most basic way to create a flow pattern in your tank; The Laminar flow uses powerheads to create a single constant flow of water. As you can imagine this isn’t very conducive to our needs. The Laminar flow type will create dead zones in your tank where nutrients can’t get to and waste can’t escape from. This type is not the optimal type of flow you should be implementing into your reef tank. You can try to create your own custom version of the laminar flow using powerheads but it will still be limited in its coverage potentially leaving dead spots.
Gyre (Or oscillating flow)
As the name suggests, Gyre or oscillating flow creates more dynamic movement within the tank’ system. This type uses wavemakers and powerheads to create its flow and is best for a lot of different types of coral since this flow can be controlled. Many aquarists agree that overall this is the best flow pattern as it is affordable and controllable. Grye flow allows for a back and forth motion of the direction to allow for a more dynamic flow pattern.
The most difficult type to make without the right equipment; Turbulent flow creates random flow patterns that make dead spots nearly impossible in reef tanks. The turbulent flow type will require that you have a particular wavemaker but if you are willing to make the investment, you will have one of the best flow types to move waste and food around in your tank without leaving dead spots that will create a buildup of waste. The back and forth motion of these flow patterns ensure that the tank is moving its entire water system around the reef aquarium. The consistent back and forth motion is really good for SPS corals that demand higher rates of turnover in their reef tanks.
How much water flow should a reef tank have?
Reef tanks rely heavily on the flow to turnover the water in the tanks but how much flow they require is dependent on the type of coral that present. Do you have LPS, soft, or SPS corals? The type of coral setup that you have in your tank will have a big influence on the level of flow that you should be setting in your saltwater aquarium. Take a look at some of the general guidelines for the different tank setups below to get an idea of what your tank’s needs might be. The more sensitive your corals are the higher turnover your tank will require so that nutrients and heat are better distributed for your corals. A reminder that these are only recommended ranges and there are always exemptions to rules. You should always research your species to ensure that you are providing them with a healthy environment.
Aim for a turnover rate between 10 and 20 times per hour
LPS and Soft Coral Tanks
Aim for a turnover between 20 and 40 times
SPS Coral Tanks
This setup has the largest range between 40 and 100 times per hour so you definitely want to check what end of the spectrum your corals would prefer to be on.
If you want a better idea of how these ranges are created, check out Reef Tank Resource’s article about determining flow rate in your reef tank!
Can you have too much flow in reef aquariums?
The type of pattern that you choose though ultimately depends on the inhabitants of your reef tank. The main objective is to ensure that that flow rate is fast enough for the fish and corals in your tank and that the pattern is allowing everything in your tank to get fresh water to them and the waste-filled water away from them.
However, don’t assume that just because you have high flow and a pattern that covers the tank that you are safe. Some fish do not like high water movement so it can be detrimental to them if you spring for the faster flow rate you can manage. Always research your specific species before implementing system changes.
Also, consider what type of substrate that you have in your tank. If the substrate is really fine, you run the risk of creating an underwater dustbowl with a flow type that is too powerful for the tiny particles.
What's the problem with dead spots?
Dead spots are areas of the reef tank that new water doesn’t reach. Essentially, it is a stagnant section of your tank that slowly collects waste, food particles, algae, and other nasties as time goes on. The waste that does collect their though will slowly mess with the water quality in the rest of the reef aquarium which is why you want to avoid doing this as much as you can while designing your flow patterns.
It might even take a little bit of trial and error as you get used to the equipment and its influence on the water. If you can manage it, you should play around with the flow right after you introduce your live rock into the tank’s system. That way you can see how the live rock plays into the overall flow of the aquarium without risking any fish or corals that you may have already introduced.
Do I need a powerhead for my saltwater tank?
Short answer, yes, or some piece of equipment that will contribute to the flow rate in your tank. Powerheads move the water within your reef aquarium to ensure that the water flow is distributing nutrients, heat, and encourage gas exchange. It also allows waste to be picked up easier by protein skimmers.
Many inhabitants in your tank need some type of flow to make sure they are receiving the necessary nutrients. Your tank’s ecosystem will not survive without flow in it so you need to begin to research what flow the planned inhabitants of your tank will need to thrive.
What size powerhead do I need?
The size of the powerhead you have will depend on the needs of your tank. The most obvious factor being just how big is your tank? A larger tank means more water that needs to be moved so a larger more powerful powerhead might be necessary.
You also need to consider the type of organisms you are keeping in your reef aquarium, as some species don’t do well with high flows and some don’t do well with low flows.
What you need to consider when you are researching equipment is will it be able to keep up with the demands of the tank. Chances are you will need more than one powerhead if your tank is large enough.
How many powerheads should you have in a reef tank?
Again, the number of powerheads will depend on the size of your tank and the type of flow that you are trying to create. Usually, most aquarists will opt for two powerheads so they have more control over direction and flow patterns.
Like I said in the previous section when you design the flow pattern in your tank try to visualize it. Is the water flow moving to all the corners of the tank? If it isn’t what will help it get there?
Just remember that too much flow can also be a problem. Always cater to the needs and preferences of the inhabitants of your tank.
Where should powerheads be placed in a reef tank?
Where you decide to place your powerhead will help to determine what type of flow that you will be able to create within your reef aquarium and make it much more conducive to tank coverage. The first thing you need to consider is what type of inhabitant you have in your tank. Do you have LPS corals or soft corals that do not need as much flow? If so, you would be better off placing your powerhead away from the coral so that it isn’t being hit directly with high flow.
Think of the other objects and creatures in your tank and how they might feel about the water flow being sent directly at them? If you have a bare bottom tank, you might consider placing a powerhead lower in the tank to help create the best flow and distribute a lot of the waste that gets dep[osited on the bottom. This will help to keep your reef aquarium a little cleaner for a little while longer.
This applies to your fish too. If you know that you have fish that hang out in a particular spot and they don’t like high flow rates then you should avoid putting a powerhead aimed directly at that spot.
You can even try creating a diagram on paper to help visualize how the water may be moving around your tank as a result of different powerhead placements. Create a few designs and take into account the objects in your tank that might influence water flow through the tank like live rock. No one design fits all for powerhead placement. You need to do some research on your specific species and apply the lessons learned here to create the best flow for your tank.
What is the best powerhead for water movement in a reef tank?
The best powerhead will be largely subjective and dependent on the needs of the reef aquarium but there are a few that can be recommended based on their features and affordability.
My top pick is the Ecotech Marine Vortech line due to its magnetic design. The electronics are outside of your aquarium which is safer and creates less clutter in and around your display tank. Second, maintenance is much easier since you only need to clean the wet-side and it can be inexpensively replaced if the blades wear or become damaged. Third, they provide a lot of control for producing various types of flow. The downsides to the Vortechs are cost and less flexible placement inside the tank.
If your budget doesn’t allow for a Vortech, I recommend the Hydor Koralia line of powerheads for their affordability, and they are known for their reliability. They are easy to position for creating the best flow patterns but they aren’t wirelessly controllable, Instead, you can be plugged into a simple controller so power can be turned on or off.
What is the difference between a powerhead and a wavemaker?
The main difference between powerheads and wavemakers is that powerheads are generally designed to have one movement direction while wavemakers are designed to create a rocking motion within the tank.
A wavemaker makes it much easier to adjust your flow type and create more desirable patterns for your reef tank for water movement. You can of course set up multiple powerheads and create a makeshift wavemaker but there is still a difference in coverage.
A wavemaker is more easily able to move the entire body of water while the powerheads would be moving only sections of the water. A wavemaker will be more expensive since it involves more pumps and features than your basic powerhead.
What is a circulation pump?
A circulation pump is another piece of equipment that facilitates flow in your reef tank. There are two types of circulation pumps that use different means to create water movement in the tank. The first is a water pump which itself comes in two types of pump. There is an inline water pump that is connected to the hose that is used to filter water. They can facilitate water flow really well and have a lot of power potential. A submersible water pump works, as you might imagine, underwater. These pumps are typically working alongside other forms of filtration systems. The air pump simply pushes air through the water to create movement in the tank.
A circulation pump offers a lot less freedom to decide where it goes in the tank compared to powerheads and some wavemakers. However, the circulation pump can facilitate water flow very effectively unlike powerheads. For more water flow coverage, you might consider a circulation pump but bear in mind where it might attach and that your tank layout will support that design.
The type of flow pattern that you choose should ultimately reflect the type of creatures that you are keeping in your reef aquarium.
For soft corals or LPS corals, it might be best to lean towards a flow rate that is lower but make sure that the flow pattern is still covering the entirety of the tank. You won’t have to worry about that with a turbulent flow but then you need to be careful that the flow rate isn’t too harsh for soft and LPS corals that need a much lower turnover rate.
Reef tanks need flow to support the life in their ecosystems. Even soft corals require that there is a flow of some sort in order to get their nutrients being as they are mostly stationary creatures. They are dependent on the flow of water to get them the nutrients they need to thrive.
Flow patterns are important but as long as all the water is moving, you are looking good. You want to avoid dead spots at all costs in your system.
SPS corals are a lot more demanding but the range in which the flow rate exists is much larger than the other flow patterns. Make sure you are researching the species of SPS coral to see if they exist on the higher or lower end of the water turnover rate.
Now that you have a basic understanding of flow and its necessity in your tank’s ecosystem, you can better prepare a flow design that will be conducive for your fish and corals.