Basic Saltwater Aquarium Husbandry and Maintenance for Seahorses and Fish

Basic Aquarium Husbandry and Maintenance

We will cover some of the basics of keeping and maintaining a saltwater aquarium for seahorses. These are some of the basics and can be applied to other saltwater aquariums and fish. There is a common misconception that seahorses are hard to keep. When one understands and meets their needs they are not difficult to keep. 

What Water Parameters Should You Test? 

Some of the basic water parameters one should test for in a saltwater aquarium include ammonia, nitrites, nitrates, phosphates, calcium, pH, alkalinity, specific gravity, magnesium and temperature. See chart below for recommended levels for most seahorses, saltwater fish, corals, and inverts. Salifert makes really good test kits and we recommend them. Another aquarium test kit manufacturer is API and Hanna. 

For checking salinity (salt concentration) in the home aquarium we highly recommend a refractometer. These are actually pretty inexpensive now days and can be found at most local aquarium stores and online outlets. Hydrometers are also available but they are less accurate and not as user friendly.

How often you should check your water parameters varies. If you are new to keeping saltwater aquarium it is best to check aquarium often to familiarize yourself with your aquarium and what is "normal" and make sure things don't get off track. Of course if you are having issues with your aquarium you should also keep a closer eye on your water parameters.

General Water Parameters for Seahorses


Recommended level

Specific Gravity



8.1-8.4 (varies throughout the day, this is normal and expected)


8-12 Dkh

Ammonia (NH3)

Undetectable (Toxic to fish and corals)

Nitrite (NO2)

Undetectable (Toxic to fish and corals)

Nitrate (no3)

(Ideally undetectable) <25 PPM

Phosphate (PO4)

(Ideally undetectable) <0.2 PPM


350-450 ppm


1250-1350 ppm


70-74 F (21-23 C) for most Seahorse Species. We keep H. comes at a slightly higher range (75-76 F). If keeping fish only (no seahorses) we recommend 76-79 F. If you are keeping peaceful fish with seahorses most handle the cooler range no problem.


Topping off Water for Evaporation

Every aquarium will have evaporation. When water evaporates salt is left behind. As your aquarium water evaporates the salinity will increase. It is very important to top-off your aquarium with fresh RODI water to maintain stable salinity and prevent the water level for getting too low. 


Water Changes

In general, once the aquarium is setup and fully cycled a 10-25% weekly water change is recommend. This means you take out 10-25% of the aquarium water and replace this with new fully mixed saltwater. It helps and may be necessary to match the temperature and specific gravity of the new saltwater before adding this to the aquarium.

Water changes help reduce nitrate, phosphate and organic build upas well as replace calcium, minerals, ect that have been used up in the aquarium. We always recommend using RODI (reverse osmosis deionized) water to mix saltwater for saltwater aquariums. Tap water and regular bottled water or spring water can have unknown minerals, nutrients ect. Tap-water whether it be well water or city water can also vary in quality and other factors. For this reason, using RODI water is key for making sure you are not adding potentially harmful substances to your aquarium. This will also help reduce algae growth in your aquarium.

Protein Skimmer

It is important to have your protein skimmer properly adjusted to maximize its efficiency. Keeping the neck of the protein skimmer and collection cup clean will allow the protein skimmer to work best. Cleaning it at least 2-3 times a week is best. You will want to go by the manufactures recommendations for properly adjusting your protein skimmer.

When you have your protein skimmer in your sump you want to make sure it is placed in an area where the water level in the sump is consistent. This will help keep the protein skimmer internal water level adjust properly allowing it to work best. 

SCA Protein Skimmer

Changing Filter Media


Using activated carbon with seahorses really helps improve the water quality long term. Activated carbon pulls out dissolved organics, will clear discolored water, pull out contaminates and more. It is safe to use with seahorses and we recommend using it in your aquarium. You do want to keep it in a mesh bag. It should be changed about every 3-6 weeks. 

Granulated Ferric Oxide (GFO)

Granulated Ferric Oxide (GFO) can be used in the aquarium to help reduce unwanted phosphates. If you have delectable phosphates you may consider using this in your aquarium. It is safe to use with seahorses. We recommend also changing the every 3-6 weeks. Like activated carbon, you want to keep this in a mesh bag in the aquarium.

Keep your Sump Clean and All in One Aquarium Compartments Clean

If your aquarium has a sump you want to keep the sump clean and detritus free. It is good husbandry to get in the habit of wiping down your sump often before detritus builds up. If your sump gets a lot of detritus build up it can create a breeding ground for bad bacteria, cause instability in the aquarium, deteriorate the water quality and more. Keeping the sump clean is key to long term success. If you find that you have a build up of detritus in your sump it is best to siphon this out rather than stirring it up. Stirring up a lot of detritus in a system can cause issues such as a pH, alkalinity, bacterial blooms or other issues. It is very important to keep your sump clean.

We recommend the same for those with All in One Aquariums. It is just as important to keep the compartments and back area of the aquarium clean and detritus free. This is key to creating a long term healthy environment for your seahorses, corals, fish and other tank inhabitants. 

If you use filter socks in your sump it is important to change them often. We change our filter socks daily at our farm. Any leftover food that goes to the filter socks is not removed from the aquarium until you remove the socks. Frozen Mysis shrimp and food will quickly spoil in the aquarium, lead to high bacterial counts, high nitrates, ect. Changing them at least a couple times a week is ideal. 

If you have an all in aquarium it helps to use filter floss in the first compartment where the water enters. Filter floss is inexpensive and great for removing large particles such as left over food. Like filter socks, the filter floss should also be changed often. 

Canister filter Maintenance 

Canister filters can work in a saltwater aquarium but we recommend having a sump if possible. If you are going to use a canister filter on your seahorse aquarium it may be best to use it for holding carbon, GFO, and media such as MarinePure media, and avoid using sponges. Sponges tend to trap a lot of waste and create a breeding group for potentially harmful bacteria and unwanted nutrients (nitrates, ect). If setup this way, you want to take the canister apart every 2-3 weeks minimum, change the carbon and GFO, shake the media around in the saltwater and make sure you are not getting detritus and waste build up.

It is VERY important to NEVER clean media with freshwater. This will kill your beneficial nitrifying bacteria and lead to an ammonia or nitrite spike. It can cause your aquarium to recycling.

Thank you very much for reading. We hope you find this helpful. Understanding how to properly maintain your aquarium is key to success. If you need help troubleshooting please reach out. One can test their water parameters and all read "perfect" and you can still run into issues. It is important to keep an open mind and realize aquariums can be complex and there are many things we can not test for that can be overlooked. We love helping hobbyist, especially new hobbyist. If you have any questions please reach out. We are happy to help and want you to be a successful keeper. Also see links to more resources below.

Contact Information:


Phone: 410-618-3604

Hours: Monday-Friday 11:00 a.m. to 5:00 p.m. EST     

Other Helpful Resources and Further Reads

Cycling a Saltwater Aquarium for Seahorses and Fish

Temperature Range for Keeping Seahorses in the Home Aquarium and Why

Water Flow in a Seahorse Aquarium

Substrate in a Seahorse Aquarium-Bare Bottom vs Sand

Choosing Your Seahorse Species and Stocking

Feeding Your Captive Bred Seahorses

Tank-Mates for Seahorses-Fish

Tank-Mates for Captive Bred Seahorses-Live Corals

Why Mixing Seahorse Species is Not Recommended