If you are planning a seahorse aquarium or think you may want to keep seahorses this article is a must read!
Seahorse Savvy is the largest producer of captive bred seahorses in the United States. We have extensive experience with several species of seahorses including Hippocampus erectus, H. kuda, H. reidi, and H. comes. In this article we hope to provide a summary of recommendations that will enable you to successfully keep one of these larger seahorse species in the home aquarium and also cover some of the common misconceptions about seahorse husbandry. Initially setting up your aquarium properly will significantly increase your chances for long-term success. This may include spending more money on the right equipment and quality livestock. While this may at first appear to be the more expensive route, avoiding shortcuts in the beginning will prevent avoidable and costly mistakes down the road.
Acquiring Healthy Captive Bred Seahorses and Setting up a Seahorse Dedicated Aquarium
While it is often stated that seahorses are hard to keep, this is a complete misconception. While some specific requirements may differ slightly, meeting the needs of our captive bred seahorses generally entails no more difficulty than keeping almost any other marine aquarium. The typical mixed reef aquarium is likely not suitable for seahorses. A dedicated system designed with the needs of your seahorses in mind usually provides the best outcomes. However, this system doesn't necessarily need to be any more complex than the typical reef aquarium.
The misconception about seahorses being difficult to keep partly stems from the historical sources of seahorses in the aquarium trade. In the past, a lot of seahorses that were available in the aquarium trade were wild collected seahorses and "net-pinned" raised seahorses. Net pinned raised seahorses are seahorses raised in nets in the ocean, not a closed system. Wild seahorses often travel for long periods of time through the supply chain before making their way to the store where you purchase them. It is hard to know what they have been exposed to and how they were cared for during this process. Wild seahorses are not accustomed to eating frozen foods and will often only recognize live food or not eat at all. Depending on collection methods and locations, wild caught seahorses may be exposes to significantly more stress than their captive counterparts. Significant stress will often prompt seahorses to stop eating. Therefore wild seahorses can be very difficult to feed. In addition, wild sourced seahorses have a greater possibility of carrying pathogens. Wild seahorses often have issues from the start making them challenging to keep even with the proper setup.
Seahorse aquaculture has advanced rapidly in recent years and captive bred specimens weaned to accept frozen Mysis shrimp are now more readily available. Thanks to new developments in nutrition, equipment, and husbandry practices, it is now exponentially easier to be a successful seahorse keeper.
Captive Bred Seahorses
Healthy captive bred seahorses like our farm raised seahorses and other farms are completely weaned to accept frozen Mysis shrimp as their staple foodsource, making feeding convenient and easy. Captive bred seahorses are adapted to life in the aquarium and can easily transition to your home seahorse aquarium. Our facility utilizes closed system and every seahorse on our farm is raised in accordance with strict bio-security protocols. In our facility pathogen risk is reduced by preventing exposure to other fish or invertebrates. Our bio-security protocols ensure any seahorses you receive from us will arrive in prime health. In order to prevent antibiotic resistance, our aquaculture methods prohibit use of prophylactic antibiotics. Instead, we utilize probiotics to encourage healthy beneficial bacteria in our systems. All fish entering our facilities are subject to strict quarantine and bio-security protocols. All of our fry and juvenile seahorses raised at our farm are treated to prevent parasites. When you obtain captive bred seahorses from our farm, they are healthy, acclimated to life in an aquarium, and completely weaned to accept frozen Mysis shrimp as a staple food-source. When provided the proper setup and care, you can expect our seahorses to be hardy and enjoyable fish to keep.
Part of Seahorse Savvy's grow-out facility
Seahorse Color-Color is NOT fixed and Changes
Another common misconceptions about seahorses regards their color. Color in seahorses is NOT fixed and changes based on mood, surroundings, lighting, and many other factors. The same seahorse can display black, brown, gray, yellow, golden, beige, and other variations of color and pattern. Some can change color quickly, others may find a color they prefer and rarely change. Color with seahorses can vary a lot. We see them change color as fast as us moving them from their holding aquarium to a shipping bag. In this case the change is a normal stress response. When seahorses are displaying and courting they also typically show color changes. Color can also change with age and many other factors.
There are several ways to encourage brighter coloration with your seahorses.
1. Utilize warm white lighting rather than a blue or violet oriented spectrum will allow your seahorses to showcase their brighter shades.
2. Install a blue aquarium background to promote more vivid colors.
3. Aquascape the aquarium with artificial brightly colored (yellow, orange, pink, and blue) coral inserts rather than liverock and sand. The typical aquarium with liverock and sand typically encourages beige or dark coloration since this is the dominate color in the aquarium.
4. Maintain stable water quality and reduce stress. Poor water quality and stress can lead to your seahorses displaying a darker coloration.
Above photo is all the same individual seahorse displaying a wide range of coloration. As one can see, color is not fixed and changes can be dramatic. Photo credit Lucie Arawana of her seahorse Jetlag.
Seahorses have a wide range of beautiful markings. We encourage folks to appreciate their individual intricate markings and personality and not get so hung up on color since it is not fixed and unpredictable at times. Hippocampus erectus, commonly called the lined seahorse are some of the most commonly available captive bred seahorses and very hardy. They make great beginner seahorses and in our opinion have some of the most beautiful markings.
Water flow is very important with keeping seahorses. One of the misconceptions we most commonly hear when speaking with hobbyists is that seahorses require low water flow. This is not at all true and in fact too low of flow will cause issues at some point.
How Much Water Flow?
At our farm, we raise our captive bred seahorses in moderate to slightly high water flow and our aquariums turn over their volumes approximately 20-25 times per hour. It is important to keep in mind that every aquarium depending on how it is setup is a bit different. We recommend aiming for turning over the volume of the aquarium approximately 10-25 times per hour. Having moderate to slightly higher water flow will prevent detritus from building up, keep dissolved organics down, allow the water to pass through filtration so it can do the work, create better gas exchange, and lead to an over all healthier aquarium. Too low of a rate of water flow will allow detritus build up over time, potentially lead to a build up of undesirable gases (high CO2, ect), allow leftover food to be more easily settle in the aquarium, cause issues with pH, and create a less healthy environment for your seahorses.
Often times to achieve good water patterns power-heads are needed. You can keep powerheads in your seahorse aquarium but you will need to cover them. If you do not cover your powerheads your seahorses can hitch to them and injure themselves! Several pump manufacturers including EcoTech Marine (manufacturers of the popular VorTech pumps) sell covers for their products which provides for a convenient and effective way to create waterflow while protecting your seahorses from injury. For powerhead models without a pre-made cover, you may need to make one yourself using material such window screen or some other mesh material.
We recommend positioning powerheads in a way that creates direct, consistent water flow. Seahorses are inherently intelligent fish and will quickly learn where the higher flow areas are and will generally avoid directly swimming in front of them. Having random flow works well in reef aquariums but is not recommend with seahorses random currents can catch them off guard. It helps to turn the powerhead setting down when you first add it to the aquarium while the seahorses learn that this is a higher flow area. It typically takes a few days to a week or so for your seahorses to learn. Once they have figured it out, then slowly ramp the powerhead up to the desired rate of flow.
At our farm, we actually find seahorses enjoy the water flow quite a bit. We observe them swimming right up to the high water flow and some really prefer to hang out in these high water flow areas. While this surprises a lot of people, there are logical reasons for seahorse's proclivity for areas of high flow. In the wild, these areas often bring large concentrations of plankton. In essence, high flow currents are often an all you can eat buffet for wild seahorses.
Rest spots-Hitching Posts
Seahorses are sit and wait predators. They use their prehensile tail to hitch onto objects. They are not active swimmers compared to most saltwater fish. For this reason it is important you provide your seahorses with lots of "hitching-posts" for them to hold onto. Hitching-posts can include yellow plastic chains, artificial branching coral replicas made for aquariums, live Gorgonians corals, and live soft corals.Often, seahorses keepers will utilize only brightly colored hitching posts as this encourages the seahorses will brighter their colors in an attempt to blend in with their surroundings. It is important to make sure the aquarium not only has good water flow, but also plenty of hitching posts to provide your seahorses areas to rest and feel comfortable as they are accustomed to.
Substrate-Sand vs Bare-bottom
Choosing whether to setup your aquarium bare-bottom (no sand) or with sand is a personal preference. There are benefits to both. Aquascaping with liverock is also important. Creating an open rock structure will allow for better water flow and help prevent detritus build up.
Having sand in the aquarium is more aesthetically pleasing to most people. You can also have a variety of sand dwelling clean up crew inverts including Nassarius snails, Cerith snails and sea cucumbers which really need a sandbed to thrive. Nassarius snails are especially good clean up crew with seahorses as they help eat leftover meaty foods. You will also have a lot more beneficial micro-fauna with a sand-bed.
If you decide to go with sand in your seahorse aquarium we recommend using an aragonite substrate in the ~0.5-1.5 mm range. CaribSea Fiji Pink aragonite is our favorite. Avoid larger substrate such as crushed coral. Over time larger substrate will allow for a build up of detritus and waste. We have seen a lot of hobbyist have issues keeping their seahorses in an aquarium with coarse crushed coral substrate.
Bare Bottom (no Sand)
Having a bare bottom aquarium (no sand) can make keeping your aquarium cleaner much easier. With no substrate on the bottom it is easy to make sure waste isn't building up in the aquarium. Build up of detritus (waste) in the aquarium creates instability and can promote nasty bacterial growth that can make your seahorses more susceptible to problems. Keeping build up of waste out of the aquarium is one of the keys to long term success with seahorse keeping.
Water Quality and Parameters
Maintaining high water quality is key to success with seahorses and any marine fish. Using RODI water (reverse osmosis deionized) or distilled to mix up your saltwater is a must. Tapwater or bottled water can contain many harmful things that you are not able to test for on most home aquarium test kits. It can also contain high levels of undesirable nutrients which can lead to algae problems and problems with your fish.
It is important to keep an open mind when it comes to water quality with your seahorses or any fish. As mentioned before, there are many things that can be off with your aquarium that we can not test for. Just because your aquarium test kits show levels in range doesn't mean the water quality is perfect. There is always room for improvement.
Reducing dissolved organics in your system is extremely important. From troubleshooting with hobbyist over the years we find high dissolved organics in a system to be one of the leading causes to issues with keeping seahorses. Dissolved organic build up in the system from waste not being properly removed. This leads to instability in the system, high bacterial counts, can effect pH, and degraded water quality. Below we will discus ways to reduce dissolved organics in your system.
Using a Protein Skimmer
We highly recommend using an over sized protein skimmer with seahorses. This will greatly reduce organic build up in an aquarium. We would not setup a seahorse aquarium without one. We recommend ideally going with a skimmer that is twice rated for your aquarium. For example, if you have a 30 gallon aquarium we recommend using a protein skimmer that is rated for at least a 60 gallon aquarium. A protein skimmer will also help prevent a build up of inorganics in your system as well.
Having your protein skimmer properly adjusted is key. You also want to clean the skimmer collection cup and neck often as it works most efficiently this way. Don't wait for the cup to fill up before cleaning. Cleaning the cup every few days works well for most aquariums.
There is a lot of misinformation out there that protein skimmers can over saturate the water with oxygen and lead to Gas Bubble Disease problems with seahorses. It is very unlikely a proper protein skimmer is going to over saturate your water with gas. Gas bubble disease is not actually a disease but rather a term to describe a set of symptoms. It is environmentally triggered meaning something is off in the aquarium that it is triggering this issue. From troubleshooting with keepers over the years the most common issue associated with Gas Bubble Disease occurring is a build up organics in the system. Once the issues are fixed and the system has been cleaned up the GBD problem typically resolves itself. Having a protein skimmer will help reduce both organics and a build up of inorganics and will help maintain high water quality. We highly recommend using one.
Hippocampus erectus juveniles
Practice Good Aquarium Husbandry
Practicing good aquarium husbandry will help reduce a build up of organics and inorganics in your aquarium. We recommend 10-15% weekly water changes. Every system is a little different and some may require more frequent water changes. The better the filtration you have and having lower stocking density will help reduce how much water you need to change. Using activated carbon will help remove dissolved organics. We recommend changing the carbon every 4-8 weeks. Using GFO (granular ferric oxide) will help keep phosphates down. We also recommend changing GFO every 4-8 weeks as well. If you have filter socks in your sump we recommend changing these often. We change our filter socks daily at our farm. If you can change yours every 2-3 days this is ideal as you do not want food and waste sitting in the system. You are not actually removing collected waste until you change the filter socks. Having a sump with filter socks is our prefer method over hang on the back filters or canister filters. If you have an all in one system with back compartments, filter floss in the first compartment where the water enters works great for catching waste. Filter floss is inexpensive and you can take this out every couple days and replace it. We also like to use MarinePure media in our sumps rather than BioBalls. MarinePure media has lots of surface area for beneficial nitrifying bacteria to colonize. Other media such as BioBalls tend to trap a lot of detritus and not provide nearly as much surface area for beneficial bacteria.
From our personal experience and troubleshooting with customers over the years, seahorses seem to be more sensitive to dosing and quick changes in pH compared to other fish. For this reason, we recommend trying to avoid dosing calcium, pH, magnesium and other buffering supplements. Most seahorse aquariums if setup and maintained properly should not need to be dosed. If kept with live corals, most are going to be soft corals which really do not pull much calcium from the water. Again, every system is a bit different in its needs but in general doing 10-15% weekly water changes should be sufficient for maintaining proper water parameters. When using a good quality salt for your aquarium it is very unlikely you will need to dose due to calcium consumption in a seahorse aquarium. It is important to note that pH in an aquarium fluctuates throughout the day from respiration and photosynthesis. This is normal and expected, do not chase the pH by dosing as it is changes, this is normal.
Temperature is very important with seahorses! For most species of seahorse such as H. erectus, H. reidi, H. kuda, H. comes, H. zosterea (Dwarf seahorses), and other species (not cold-water species such as H. abdominalis) we highly recommend keeping your aquarium between 70-74 F. This is a cooler temperature ranges than recommended for most saltwater aquariums. Seahorses have a primitive immune system and for this reason are more susceptible to bacterial related issues compared to other fish. Keeping your aquarium temperature in this cooler range will help keep down harmful bacterial counts such as Vibrio sp. and therefore reduce the likelihood of your seahorses coming down with bacterial related issues. Keeping the temperatures in this cooler range also seems to reduce stress in our experience.
Choosing Your Seahorse Species and Stocking
Mixing Seahorse Species
We do not recommend mixing different seahorse species in the same aquarium. Seahorses from different areas of the world carry different micro fauna (bacteria, ect). Seahorses can have immunity to these and when introduced to another species which has not been previously exposed and with no immunity it can cause stress on the immune system. This can directly cause issues with them and also make them susceptible to other bacteria or issues that may normally not be harmful. Seahorses have a primitive immune system and are more susceptible to bacterial related issues compared to other fish which likely has to do with why we see this issue.
In short, mixing different species often results in one or both species not doing well. Sometimes issues happen right away and other times it happens months down the road. Some keepers are successful at mixing species but from troubleshooting with hobbyist it seems to rarely go well when mixing species in the same aquarium. Hobbyist often ask us why it matters if all the seahorses are captive bred and from the same farm. We do not mix species at our farm for this same reason. Different species are kept in different systems.
One exception to mixing species is H. Reidi and H. Erectus. These two species naturally overlap in their distribution. There is evidence these two species naturally hybridize too. We have successfully kept these two species together at our farm for years with no issues. Many other hobbyist have as well.
Having an idea of the number of seahorses you wish to keep is helpful when you are choosing your aquarium. For the larger seahorses species we generally recommend a 30 gallon minimum aquarium size for the first pair of seahorses with an additional 15 gallons for every additional pair you wish to keep. A larger aquarium if possible is even better. Seahorses really enjoy having space and will use the whole aquarium. Having extra water volume can create a more stable environment as well. While 30 gallons is the minimum recommended aquarium size a 40-50 gallon aquarium size would be even better.
A common misconception is seahorses need very tall aquariums to thrive and breed. Seahorses are vertically oriented fish with most aquarium kept species reaching about 5-7 inches in height. 18-30 inches deep works well for seahorses. When choosing and aquarium and what height to go with keep aquarium maintenance and cleaning in mind. 30 inches or more is very deep and can be difficult to work in when you are doing your regular maintenance. A lot of keepers do not take horizontal space into consideration. Seahorses like to move around and use their horizontal space as much as their vertical space. You don't want to cut them short on horizontal space by choosing an aquarium that is very tall. We prefer aquariums 18 inches or wider.
A lot of hobbyist do not realize how large seahorses can reach with maturity. As mentioned before, H. erectus seahorses for example, reach 5-7+ inches as adults. At this size they are pretty large fish hence the aquarium size recommendation. Seahorses eat more than the typical saltwater fish and are messy eaters.
Overstocking can lead to many issues. When the density is too high a build up of organics is likely to occur. Seahorses really like space and to not be over crowded. Crowding can cause stress as well as instability in the aquarium. It will be much more challenging to maintain high water quality when the aquarium is overstocked.
It is important to avoid aggressive fish with your seahorses! Seahorses are fairly slow moving and don't always pay attention to the warning signs of other fish. With their sit and wait behavior it is easy for them to get into another fish's territory and be a target for aggression with other fish.
Seahorses are also slow eating compared to other fish. For this reason large or fast eating fish can out compete your seahorses for food. Making sure your seahorses are getting their fair share to eat is very important.
Small peaceful fish such as gobies, cardinals, and others are recommended if you would like to have other tank-mates with your seahorses. There is a large variety of gobies that are seahorse suitable tank mates. These little fish have tons of personality which is why they are one of our favorite seahorse tank mates. When possible, it is safe to stick with captive bred fish with your captive bred seahorses. This can reduce the chances of introducing pathogens to your seahorses.
For more detailed information about seahorse suitable fish tank-mates see our article "Tank-mates for Seahorses-Fish" here: https://seahorsesavvy.com/blogs/news/tank-mates-for-seahorses-fish
Seahorses are very personable and easy to fall in love with. Many hobbyist keep them species only (no fish) and this can make for a very nice display for these stunning animals.
Tank-Mates-Live Corals and Macro Algae
While seahorses can be kept in an all resin artificial coral tank some hobbyist prefer a more natural look. Having live corals and macro algae in the aquarium can create an absolutely stunning display. There is a huge diversity of corals that are seahorse safe and hardy species to keep. There are also many corals that can sting your seahorses so you want to be familiar with corals species and which are safe and which are not.
Soft coral and macro algae seahorse display. Photo credit Teven. L in Singapore.
Seahorse Safe Corals
In general, most soft corals including leather corals, mushroom corals (Discosoma sp., Rhodactis sp. Ricordea sp., ect), zoanthids, Green start polyps, Xenia, Clove polyps, and more. Our favorite live coral with seahorses is photosynthetic Gorgonians. These are hardy corals if given proper lighting and water parameters and make great seahorse hitching posts as well. Our seahorse love them!
Some stony corals such as Micromussa, Favia, Favites, Alveopora, Goniopora, and Montipora typically do not have a strong sting and may be seahorse safe. There are certain stony corals we have successfully kept with seahorses over the years including these mentioned. Stony corals are generally a bit more sensitive to water quality and lighting compared to the soft corals. If you are new to corals and seahorses it is best to stick with the soft corals mentioned above while you are familiarizing yourself with care and differences with species.
Corals to Avoid
There are many corals that can sting your seahorses! These corals need to be avoided in your seahorse aquarium. Seahorses again, are slow moving and can be easily stung compared to other saltwater fish. Corals such as Euphyllia spp. (Hammer coral, Frogspawn, and Torch corals), Galaxea, Symphillia, are known for having a strong sting.
Other large polyped stony corals such as Scolymia, Acanthophyllia, really large Fungia, Helliofungia, often have feeder tentacles that can be sticky when out and could grab or sting your seahorses and cause harm. Coral in these genera should be avoided with seahorses.
While not a coral, anemones also have a strong sting and are not seahorse safe.
For more detail information on seahorse safe corals seahorse our article "Tank-mates for Captive Bred Seahorses-Corals" here: https://seahorsesavvy.com/blogs/news/tank-mates-for-captive-bred-seahorses
There is a large variety of live macro algae available for salt water aquariums. Many of these are easy to keep and can provide natural hitching posts for your seahorses. They are of course photosynthetic so one must have proper lighting to keep them. Macro algae can help reduce nutrients in the aquarium as they use them to grow. Some of our favorite varieties include Caulerpa prolifera, red dragons breath, branching coralline, and Halimeda sp. Some macro algae such as C. prolifera and some Halimeda sp. are rooting varieties and need substrate. Having a macro algae dominated aquarium can really make for a unique and stunning display.
Gorgeous macro algae disply. Photo credit Lucie Arawana.
Clean up Crew
Having a good clean up crew in your seahorse display tank will help keep things in check. We recommend having a mix of scavengers and algae eating invertebrates. Nassarius snails are one of our favorite inverts for clean up crew in a seahorse aquarium. These sand dwelling snails will come out when they smell meaty food and help keep left over Mysis shrimp out of the aquarium. Cerith snails, another sand dwelling snail, are great for algae and consuming detritus. Margarita, Astrea, and Turbo snails are also some great algae eating snails. Blue leg hermit crabs are seahorse safe and can make great clean up crew for both algae and leftover food. Some seahorses will learn they can eat them! Peppermint shrimp are great for clean up crew too. Large individuals are usually fine, your seahorses may find small peppermint shrimp as a yummy snack. Having a well mixed clean up crew will help keep your seahorse aquarium healthy and clean.
Feeding your seahorses properly is very important. Captive bred seahorses like ours are completely weaned to frozen Mysis shrimp, specifically Hikari BioPure and Piscene Energetics Mysis shrimp. You can diversify their diet by offering them frozen Spirulina enriched brine shrimp, enriched live brine shrimp, and plankton, amphipods. While it is good to add diversity of to their diet we recommend 90-95%+ of their diet be Mysis shrimp. Mysis shrimp is very nutritious for your seahorses.
Non-enriched brine shrimp is very lacking in nutrition and we commonly hear of people mixing this up with Mysis shrimp. Mysis shrimp is what you want to feed your captive bred seahorses. Since our captive bred seahorses are completely weaned to frozen Mysis shrimp they often times will not show interest in other foods such as brine shrimp, copepods, ect.
There is a common misconception that seahorses have no stomach and need constant feeding to thrive long term in an aquarium. While seahorses do have a quick metabolism and need to be fed often they do not need a constant supply of food. Twice a day feedings with the larger seahorse species is sufficient. One feeding in the morning and one feeding in the evening is recommended. If you are able to fit in a third feeding that is great but if not two feedings a day is usually plenty. We recommend feeding them 2-3 times daily with at least 6 hours between feedings to give them time to digest.
In general, a pair of seahorses can typically eat about a cube of frozen Mysis shrimp per feeding. This varies with individuals, age and if they are breeding but it is a good starting point. The goal is to give them enough to finish up within 15-30 minutes. You do not want to leave uneaten food in the aquarium for more than a half an hour. Like any raw seafood, Mysis shrimp will begin to spoil quickly.
Rinsing Mysis Shrimp
Rinsing your Mysis shrimp before feeding is good practice. Thaw out enough frozen Mysis shrimp for a single feeding. After it is completely thawed pour the Mysis shrimp through a fine mesh net and rinse under cool water. This will help rinse off fine particulates and help keep your aquarium much cleaner.
Unrinsed Mysis Shrimp Rinsed Mysis shrimp
Free feed or use a Feeding Station with Your Seahorses
Seahorses at a feeding station. Photo credit Lisa B.
Some hobbyist prefer to "free feed" their seahorses by pouring in the thawed Mysis shrimp and letting the seahorses feed in the water column. This works for some hobbyist, especially those with larger herds, but you want to be careful to not get a lot of lost food in the aquarium. You can also waste a lot of food this way if it is going right into the filtration or filter socks. Also keep in mind uneaten food sitting in the filtration will begin to harbor a lot of undesirable bacteria. Having a lot of water flow to keep the food suspended and good clean up crew is key with this feeding method.
Many hobbyist prefer a "feeding station" where they spot feed their seahorses. This method does require some training and can take a couple weeks for your seahorses to learn. Once your seahorses figure out how to use the feeding station it can really help keep your aquarium cleaner and your seahorses well fed.
Any cup shape object safe to go into the aquarium will work. It helps to have the feeding station in a lower flow area with plenty of hitching posts for the seahorses to hold onto while feeding. To feed them at the feeding station you simply target the thawed Mysis shrimp into the feeding station using a turkey baster.
To learn more about training your seahorses to feed from a feeding station see our article Training Your Seahorse to Feed at a Feeding Station here: https://seahorsesavvy.com/blogs/news/training-your-seahorse-to-feed-at-a-feeding-station
We hope you find this article and tips helpful. Seahorses are a lot of fun to keep and with the proper setup do very well for keepers. With proper care one can expect their seahorses to live 4-7+ years on average. If you have any questions we are happy to help and please reach out.