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Flow in a Seahorse tank

“Flow is one of the most important, and yet least understood aspects of a seahorse tank” was the response Abbie Underwood of Seahorse Source gave when asked which flow rates were best for a new seahorse display.  Her quote and advice come to mind every time I am asked about flow in a seahorse tank, because the comparison she made really helps the average hobbyist understand more easily.  The entire explanation and Comparing flow to a kitchen sinkdemonstration can be seen in my video “How to set up a Seahorse Tank” (Click on the link to watch this portion of the video).  Basically, she demonstrated how “breaking up the flow to reach every area of the aquarium will provide a healthier environment”.  Using the example of cleaning a kitchen sink, she illustrated that in any situation where we need to clean multiple surfaces, one directional flow will not cut it.  I have also personally experienced the difference in seahorse activity and health, along with ease of maintenance, when more combined flow is added to an aquarium.  We will cover all of this information in the following article, along with answering the questions most frequently asked about flow.

What is “flow” anyways, and why is it important in a seahorse tank?

The basic definition of flow in the saltwater hobby is the amount and way water moves through an aquarium.  Sounds simple right?  In reality, flow is extremely important and affects so many other aspects that Adam Blundell, M.S. wrote an entire series to explain, called “Lateral lines:  Water Flow” in the Advanced Aquarist online magazine.  The series covers the different types of flow produced in an aquarium, the reasons why flow is so important, and (the most valid point in my opinion) is that many different factors go into determining which type of flow will work best in a specific situation or aquarium.  The size and shape of the tank, type of flow, what is producing the flow, along with the specific needs of the inhabitants matter a great deal in deciding how to provide adequate flow to an aquarium.

CB Seahorses
A breeding tank with no rock in the display

In most articles dealing with recommended flow rating in a seahorse tank, the “turnover rate” is typically the only type of flow considered.  While the term “turnover rate” was meant to describe how many times the water is turned over in the tank overall, many people believe this only includes the main filter.  The main filter’s turnover rate IS important because it is the amount of times the mechanical and biological filters get to clean the water before returning it to the aquarium.  Many seahorse tanks are set up with little to no rock, and are dependent upon water reaching the good bacteria and equipment in the sump or hob.  In these situations, making sure the filter is rated correctly affects everything from the good bacteria’s ability to keep a tank free of ammonia, to the skimmer’s ability to remove organics.  If the HOB or pump’s turnover is too fast, some water will be pushed back into the aquarium without being cleaned thoroughly.  Too slow, and organics will build up within the aquarium because the water is not being cleaned enough times each hour.

In seahorse tanks with a lot of rock, the bacteria within and upon the rock can still only filter the water it comes in contact with.  If water is not being pushed through and around the rocks, it’s not being filtered.  And, the mechanical filters such as skimmer, scrubber or socks can only clean the amount of water being fed through the HOB or pump.  So, the guideline of 10-20 times turnover in a seahorse tank provides an adequate goal in terms of the actual amount of water that needs to be run through the filtration system.  However, the return of water from a HOB or sump being constant and in one direction means that more flow within and throughout the tank is needed to create a healthy environment.  As abbie pointed out, “breaking the total flow goal up to include unidirectional flow in addition to turnover will provide a healthier environment for the seahorses”.  So, the guideline I recommend is 10-15 times turnover via HOB or sump, with an added 5-10 times circulated within and throughout the aquarium.  Followed by observations and adjustments based on the seahorses’ reactions.

Why is this the guideline?

In an Advanced Aquarist article, J. Warrick discusses the many reasons that water movement is extremely important in any saltwater aquarium, including gas exchange, removal of waste products, carrying food to filter feeding organisms throughout the tank and removing excess food before it becomes food for pathogenic bacteria.  He also points out that aquatic animals have evolved to thrive in specific water flow environments, indicating that the intensity of flow in the area which the animal is found in can provide a clue as to which flow rates are best for the specific fish. (Warrick).  Seahorses are found at many depths in the ocean, but most often they are seen residing in shallow coastal areas.  The flow of water in coastal areas is typically more turbulent and moves in many different directions due to waves and currents crashing into each other, versus the laminar flow at the bottom of the ocean that moves in one direction.

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Based on this information, we should provide a seahorse tank with a lot of water movement in many directions, instead of the old theory that a “low flow environment is best”.  This not only provides seahorses with the water movement similar to their natural environment, but also helps tremendously in avoiding organic build up by eliminating dead spots.  Basically, all of the extra food and waste found in a seahorse tank will not be able to build up if there is enough flow to stop it from settling anywhere.  In my personal opinion, seahorses will also remain healthy for a longer amount of time when they are encouraged to move around more, and they look so pretty and happy when they flow dance :)!

The actual 10-20 times turnover guideline found on most seahorse websites is based on professional breeder and long-term seahorse keepers sharing what has worked best for them.  I can personally vouch for the accuracy, as I follow these guidelines in my many seahorse tanks.  However, the way to achieve these flow rates is not very clear in many articles.  We will dig deeper into the reasons that more combined flow is my personal favorite option.  Seahorses are not as delicate as they have been portrayed, and while they do have specific needs, low flow is not one of them (excluding hippocampus zosterae – dwarfs – who do need a much lower flow rate).

My personal experiences with seahorses and flow are a prime example:

When I first started with seahorses many years ago, every article that I found online indicated that seahorses needed a low flow environment.  My first seahorse aquarium had limited water movement, and the seahorses could easily swim around with little to no effort.  The tank was a 29 gallon basic set up, with a HOB (hang on back) filter rated 300 gph (gallons per hour).  The biological filtration included cycled rock and macroalgae, but the only mechanical filtration was floss and sponge in the HOB.  According to all of the online articles, this was an adequate environment for seahorses, and they should have been happy and healthy.  Oddly enough, the seahorses chose to remain hitched and almost hiding most of the time, only moving around when it was feeding or courting time.  Based on the little research available on seahorses, I assumed this was normal and that seahorses were just not very active.  However, the seahorses literally looked bored, and the macroalgae began quickly covering with cyanobacteria and nuisance algae.  I spent the next year trying to maintain my beautiful macroalgae seahorse display, by using a turkey baster to remove all extra food and nuisance algae on a daily basis.  It was not much fun and an endless task.

A friend and future mentor finally asked about my flow rates and nutrient removal system.  He quickly walked me through adding a sump to hold a skimmer and algae scrubber, which made a huge impact on nutrient removal and cut my maintenance schedule in half!  Still, I truly believe that the biggest change that helped my seahorses’ amount of activity was adding a covered powerhead.  The seahorses almost immediately began swimming in front of the powerhead, and from that day forward, began looking much healthier and more active.  (Pulling older pictures for this article, I realized how much they love flow!  They were constantly in front of returns after I added them)


Seahorses after I added flow!

The nuisance algae became much less of a problem, and my maintenance routine was considerable less difficult.  When I decided to begin breeding seahorses and upgraded the non-breeders to a larger 60g display, I added a better adjustable pump in the sump, and 2 covered RW4s to provide a lot more multi-directional flow.  The seahorses became even more active, and began acting like the happy water puppies they have become.  They wanted more flow, and I am so glad that I was able to give it to them.

Products mentioned:

What is meant by “combined flow”?

Combined flow means that in addition to the making sure that the water is run through the biological and mechanical filters in a hob or sump 10-15 times an hour, an additional 5-10 times unidirectional flow is added for circulation.  The combination of flow from the return and a spray bar, powerheads or wavemakers distribute the flow more evenly throughout the tank, eliminating dead spots and creating a healthier, more natural environment.  Let’s look at a specific example.  In the 60 gallon tank, the goal turnover rate (10-20 times) is 600-1200 times per hour.  Many people would buy a sump pump or hob rated 600-1200 gallons per hour in order to reach the goal.  The only circulation within the tank would come from the return, leaving a lot of areas in the tank without much flow.  Instead, I would advise using a 600-800 gph pump or HOB for turnover, and adding a gyre or two wave makers rated 300-600 gph for circulation within the tank.  Providing low flow areas for seahorses to rest can be accomplished with ornaments, rock or other decorations like macros.  Another idea is to use more than one return, or a split return, so that water is dispersed more evenly throughout the tank. All of these ideas require that head pressure be considered, but we can look at that option in a later article about equipment and set up.

How to achieve combined flow?

Seahorse inspecting a covered intake

Now that combined flow makes sense, the decision remains whether to use a powerhead, wavemaker or gyre, and how to position them within the tank.  Powerheads can be tricky, because they will still only provide a continuous stream of one-directional flow.  I have found a few ways to make them work, by pointing one up and one down, or pointing them at each other. While this is better than nothing, the flow is very strong where it comes out of the powerhead and gets weaker as it travels through the water.  For these reasons, I recommend choosing wavemakers or a gyre when possible.  The wavemakers have wider openings to provide water movement that is more evenly distributed.  The brands that come with controllers include even more functions, like options to pulsate, switch the direction of the flow at timed intervals, and many other ways to recreate a pattern of flow instead of one continuous stream.  The gyre is the best option, because it creates a circular flow movement, providing the most circulation and surface agitation.  However, it might be too strong in a smaller tank. My favorite option for the smaller tanks or quarantines are the internal filters with spray bar.  There are multiple ways to recreate the seahorse’s natural environment by playing with the positioning of equipment.  The important point is to be sure that combined methods are used to recreate that surging flow and provide the best circulation possible to the aquarium.  And of course, always cover any openings that seahorses could fit their tails into!

There are many ways to cover the powerheads, wavemakers and gyre.  Most of the time in this hobby, there are multiple ways to make things work.  Just aim for a method that does not restrict the flow too much, but also protects those precious seahorse tails!  I personally use mesh with zipties or sponge as seen below:

In a smaller system, the term “adjustable” can mean many different things, so be sure to read the description before buying an adjustable filter.  On many filters and powerheads, this will just mean you can adjust the amount of flow produced, as seen here.

I really like the wavemakers that have feed options.  This allows me to cut water movement in half by temporarily disabling the the wave makers, without worrying about remembering to turn them back on.  The controller knows to start back up after the 10 minutes of “feed time”.

Why do so many other articles say seahorses need a “low flow environment”?

Simply put, recommendations change based on new information, so making sure that the article is current is extremely important before following any advice.  Hobbyists have different goals when setting up an aquarium for seahorses, but the one thing most hope to achieve is creating an environment in which the seahorses can thrive long-term in captivity.  The “basic guidelines” found on most seahorse sites are a collection of recommendations from seahorse keepers and breeders who have had long-term success using similar methods, equipment and ideas.  Understandably, these guidelines can change over time, as more information is learned through new experiences and research.  The changes do not invalidate the older ways of doing things, because the basic requirements remain the same and work.  The wonderful thing about the saltwater and seahorse communities is that the share of information allows hobbyists to start with guidelines that are proven to work, and expand upon them with new experiences and information.  Often, this leads to finding even better ways of providing conditions that are healthier for the seahorses.

The unique shape of a seahorse and their unusually placed side fins to maneuver led people to believe that they needed a low flow environment, without a lot of turbulence.  The seahorse’s ability to “ride the waves” was underestimated, even though we now know they are found in very high and low flow areas in the ocean.  Obviously the confinement of an aquarium means we cannot duplicate an ocean environment exactly, so finding a “sweet spot” in which the benefits of providing enough flow are not outweighed by conditions that prevent a seahorse from swimming around.  That sweet spot can be found quite easily by using combined methods and different sources of water movement.   

Hearing that seahorses can handle and will actually do better in a moderate to high flow environment (with low flow spots to rest) might not be enough to help you determine rates.  Please follow along in the #seahorsereef build starting next week.  I will demonstrate exactly how flow rates can be determined by aiming for the goals, and then observing the seahorses.  In this series, you will get a literal day by day view of the set up, reasons for certain products and methods, and even how I deal with new seahorses.  I am thinking of even leaving the gopro running when I’m not near the tank, so that we can all see how every change affects the new seahorses.  Please be sure to subscribe on Youtube and give feedback as this series develops!  All comments, suggestions and questions are welcome!