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Tank Setup for Seahorses

You are here: Mary St Pets > Aquarium Fish > Marine Fish > Tank Setup for Seahorses

Preparing your Tank for Seahorses

The following information is intended only as a guideline for setting up your Seahorse tank. These guidelines are deliberately brief and don't include how to set up a marine fish tank as this information is already available in any good marine tank book or pet shops. If you haven't set up a marine tank in the past, you'll find that you get the best results if you learn about basic marine tank set up for yourself as you're the best person to care for your seahorse. Your seahorse looks to you to correctly maintain their environment.

Tank Size

We recommend bigger rather than smaller, preferably a tank that is between 150 to 200L of seawater. The temperature in smaller tanks will have a higher variation between night and day. Your seahorse will be less stressed with a more constant environment where the temperature doesn't fluctuate. Yes your seahorse can cope with temperature variation in the short term, but for a happy, healthy, long life, stress free is the key!


Give thought to where you set up your seahorse tank before you fill it with water. Once filled, it is difficult to move. Avoid positioning your tank close to a window. Too much sunlight is a stimulus for algae to grow and excessive cleaning of the glass will be needed. In addition, if the window that your seahorse tank is in front of gets afternoon sun, then your seahorse tank will most likely over-heat in summer. Place your tank away from windows.

At Mary St Pet we only sell tropical seahorses as these have proven to be the easiest temperature to maintain for the home hobbyist. Please remember, however, that in summer when the temperature in Australia can reach 45°c, your home tank will heat up past tolerance point for tropical seahorses. So position your home tank in a room with air conditioning for those hottest days. Avoid putting tanks close to heaters/fires and in the direct draft of air-conditioners.

Tank Mates

Live rock is not recommended. Live rock has many benefits in home aquaria however it is not essential. On the positive side it provides biological filtration, but on the negative side it can harbour dangerous animals. Caution is required before adding live rock to aquaria as it often contains animals that will harm your seahorse, particularly shrimp, crabs and stinging polyps. Live rock also provides a mostly dark brown coloured background that will cause your seahorses to lose their bright colours in order to blend in and they will become dark brown. We have had a great deal of feedback on this point over the years, that compels us to recommend other forms of filtration that are available in pet shops or aquarium stores.

Remember that however big your tank is, your seahorse is in a confined area together with the tank mates that you choose. Most salt water fish are aggressive or too quick and will beat your seahorse to the food. In addition, most of the other salt water fish are wild and so can carry the risk of disease that may affect your cultured, disease free seahorse. For these reasons, the only species that we recommend for tank-bred seahorses are pipefish and peppermint shrimp.

Corals generally need high flow rates, which are incompatible with seahorses. In addition, some have stinging cells that can affect your seahorse. Anemones have stinging cells that can affect your seahorse and crabs and shrimp with big nippers, will also cause harm.

Water Source

In most major cities in Australia, home delivered salt water is available. This takes all the pain out of saltwater aquarium keeping and is simply the easiest way to go. If this isn't available to you, artificial sea salt can be purchased from any pet store. As long as your tap water is a good quality and you are careful to follow the instructions correctly, artificial seawater is a good alternative. Salt water from the ocean is also an alternative, but needs to be treated prior to use in your tank as per marine keeping books.

Water Parameters

Use a floating hydrometer to maintain salinity at 1024.0. Measure this once a week and top up with dechlorinated fresh water as necessary to keep the salinity relatively constant. Remember, your seahorse needs a stable environment.


Maintain the pH in your tank between 7.9 and 8.4. Don't stress too much over pH. Relax – your seahorse will tolerate pH 7.9 indefinitely with no trouble. These seahorses have been raised for many generations at this pH. If it drops below this point, and your tank isn't overstocked, it is time to do a water change. If you keep to recommended stocking densities for your tank, and do a 10% water changes every fortnight, your tank pH should never become a problem.


The optimum temperature range is 25°c – 28°c. Your seahorse will tolerate up to 32°c, but no fish will tolerate rapid and continual change. Try to keep the temperature stable and avoid any sudden changes in temperature that may occur from things like a water change, a cold night or a hot day.


You ammonia level in the tank should be nil. This is perhaps the most important parameter and should be measured daily during tank setup and then at least once a week after your tank has been established. Your seahorse will tolerate small amounts of ammonia (i.e. 0.5mg/L) for a short time (a week or two), but prolonged exposure to low levels of ammonia will cause stress, which may result in disease. The answer is to "age" your tank for 6 – 8 weeks before adding your first seahorse. Then the key is to do it slowly. The temptation is to stock your tank with lots of seahorses straight away. Avoid this at all costs – sudden overstocking of your tank will cause an ammonia level to increase, causing distress to both you and your seahorse. Initially buy one seahorse – wait several weeks and when the ammonia level drops to zero, add another. Continue until you have reached the recommended stocking density – no more.


These will build up over time but are not toxic. They will cause excessive algal growth, which is easily kept in check by regular water changes (at least 10% every 2 weeks).

Flow Rates

Flow rates can vary a great deal but a good rule of thumb to aim for with flow rates is a 200%, of your tank total capacity exchanged through your filter per hour. Strong flows associated with reef tanks are not appropriate for horses.

Tank Furniture

Your seahorse will always need a hitching post. Amongst other things we use marine grade rope. It has the advantage that it doesn't break down in salt water and is a brightly coloured background. As your seahorses will try to change colour to blend in with the background, the bright colours of marine rope will help your seahorse to retain its bright colours.

The heater that you use in your tank should be either set up to operate in a separate sump, or if it is positioned in the tank with your seahorse, you will need to cover it with a guard to keep your seahorse from grasping the heater with its tail and causing a burn.

Indoor Air Quality

Remember that anything you spray into the air in the room where your seahorse tank is positioned, will be immediately bubbled into the tank water along with your tank aeration. Many sprays have the potential to harm your seahorse. These include insecticides, air fresheners, incense, hair spray and cigarette smoke. It is best to not allow any of these substances in the room occupied by your seahorses.

Please note that the advice presented on our site is intended to be used as a guideline only and includes techniques that in our experience have been successful. Many variables may affect the condition of your water and we recommend that you seek advice should you become worried about the health of your fish.

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