Can Ocean Water Be Used in an Aquarium?

An aquarium is not only a beautiful and fascinating addition to an indoor space but is also easy and fun to maintain. It gives lovers of aquatic life an excellent opportunity to create and observe another world. They can learn about different aquatic creatures and observe their behavior.

While aquarium maintenance is generally easy, choosing the right type of water can be tricky for aquarium owners.

Many aquarium owners often wonder if they could use ocean water for their aquarium.

It is quite relieving to learn that if the owner has access to clean ocean water, there is no harm in using the ocean water for their saltwater aquariums. In fact, there can be many advantages to using ocean water for your aquarium. The dissolved minerals and salinity levels may vary in different areas, but ocean water is the natural habitat of most aquatic animals. This makes it an even better option than fresh tap water or salt mix for your aquarium.

If you collect ocean water and treat it properly, it is better than using synthetic salts available in the market. Not only can it be easier to use than the other options available, but it also helps you save money.

Providing the aquatic animals in your aquarium with similar conditions to their natural habitat can help keep them healthy.

Collecting Ocean Water for Your Aquarium

The ocean water that you collect for your aquarium must be clean and free of pollutants.

If you have a boat or can go on a water collection trip with someone, you should go off-shore to collect uncontaminated, clean water.

However, if going off-shore is not possible, you’ll have to find a place near the shore that does not have pollutants or industry or agricultural runoff.

This means that you’ll have to find an area with:

  • No nearby streams or rivers
  • No industrial discharge
  • Appropriate salinity level
  • Presence of other healthy aquatic life
  • Minimal or no boat traffic

It is best to collect ocean water during high tide because it brings fresh seawater to the shore. If it is possible to take a short trip off-shore, then collect water at a distance of one mile from the coast.

Treating Ocean Water for Aquarium

The ocean water teems with life, and it includes a diverse range of living organisms like plankton. The changing levels of pH, salinity, nitrates, nitrites, temperature, etc. in aquarium water are generally not suitable for plankton.

If the unstable aquarium conditions cause the death of plankton, there can be a dangerous spike in the ammonia levels of your aquarium. It is, therefore, essential to treat the ocean water first and make it suitable for your aquarium to prevent such issues from arising.

There are two different methods of treating ocean water for your aquarium:

Method 1 – Filter and Store Without Light

Filter the ocean water through the finest sieve you can find.

Now, keep the water in an unheated, food-grade container for a few weeks. Allow no light to reach the water inside the container. This will kill most of the plankton in the water.

You will notice a layer of debris at the bottom of the container created by the death of organisms in the water. The next step is to filter this water again carefully into another container without disturbing the bottom layer of debris. Now, aerate the filtered water for a few hours and maintain its temperature appropriately.

Take water tests for pH, alkalinity, salinity, ammonia, nitrites, and nitrates. Make any adjustments if needed before transferring the water to the aquarium.

Method 2 – Using UV Sterilizers

Alternately, after you’ve run the water through a sieve, make it pass through a reliable UV sterilizer a few times.

The next step is to keep the water in a container overnight, allowing no light to reach the water inside the container. This will make the debris to settle down at the bottom of the water.

Filter the water again and run it through a UV sterilizer one more time. Aerate the water and maintain the temperature appropriately. Take water tests for pH, alkalinity, salinity, ammonia, nitrites, and nitrates. Make any adjustments if needed before transferring the water to the aquarium.

After using one of these methods, your treated water should be ready to go into your aquarium. You can use this treated water for aquarium water changes like one would use a synthetic salt mix.

Measuring the Salinity of the Ocean Water

Salinity is the amount of salts dissolved in water. There are typically two ways to measure the salinity of the ocean water you have collected and treated for your aquarium. You can do so by using a refractometer or hydrometer.

A refractometer measures the refraction of light through a small sample of water. The display screen will display a ‘per mil’ value, which means the parts per thousand with a ‰ symbol.

The seawater has naturally 35 ‰ of salt in it. Now, the ‘per mil’ value of water refraction is expressed in numbers without any unit.

A hydrometer is another way to measure the salinity of the water. It is a less accurate way, but it still gets the job done. It is used to measure the density of water. Water naturally has a density of 1000 gm.

The presence of salt increases the density of the water, which in turn increases the weight of water slightly. You can use a plastic swing-arm hydrometer as they are easier to use. Ensure that there are no air bubbles on the arm as they can distort the reading of the hydrometer.

Topping off your Aquarium

Topping off is adding fresh water to make up for the loss of water from evaporation in your aquarium. When the water evaporates, it leaves behind salts, which can increase the salinity in the aquarium.

To bring the salinity back to an appropriate level, you will need to add fresh water. When topping off your aquarium, you can use RO water to avoid adding minerals with the water.

You can mark the water level on the glass of the aquarium to give you a general idea about water loss after a few days. Despite the decrease in the water level, you should still measure the salinity of the water with a refractometer or hydrometer.

While salt does not evaporate with the water, it is sometimes lost slightly by salt creep.

It is essential to be able to differentiate between topping off and changing the water. Topping off does not involve removing the collected waste from the aquarium. For changing the water, you will have to siphon out some amount of water from the aquarium and replace it with new ocean water.

You need to change the water regularly to maintain an appropriate environment inside the aquarium. While for topping off, you add RO or treated ocean water to the aquarium to make up for the loss of water in evaporation.

Related article: How Often to Change the Aquarium Water?

Challenges of Using Ocean Water for Your Aquarium

If you live in a coastal area and have easy access to ocean water, using it for your aquarium can be an excellent option.

However, despite the ease and its many advantages, using seawater for the aquarium has its drawbacks as well.

Finding Access to Clean Ocean Water

One of the biggest challenges of using ocean water for your aquarium is finding an easy-to-reach source of clean seawater. While there is a lot of clean water in the ocean, it is not easy to collect for everyone.

The inshore water is easy to reach, but it likely has pollutants and contaminants. Sewage, industrial, and agricultural discharge, and marine fuel residue can all add up in making the inshore water polluted and not suitable for aquatic life to survive.

For this, most aquarium owners have to collect ocean water from as away from the shore as possible. This can be significantly challenging for people who do not own a boat or have any other means to go off-shore.

Logistical Challenges

Another drawback of using ocean water for aquariums is the difficulty of taking the collected water back to your place. This can become even more challenging if you have a huge aquarium.

Aquarium owners collect ocean water in 5-gallon buckets, trash cans, watertight containers, etc. to carry it to their aquariums. After collecting water, transferring these containers from a boat to a vehicle and then to your house can be an arduous task.

Preparing Water for Aquarium

Natural ocean water requires a lot of pre-treatment before you can add it to your aquarium. Ocean water poses the risk of introducing unwanted micro-organisms invisible to the naked eye to the aquarium environment.

Usually, treating the ocean water by any of the two methods kills most of the micro-organisms and plankton, but sometimes they still survive. Running the water through ultraviolet sterilizer and using other water treatment techniques can be both difficult and costly.

Using ocean water for your aquarium is a very viable option, and if you have easy access to it, it can save a lot of money.

But, using ocean water for aquariums require the collection of water, careful treatment, topping off, and maintenance of appropriate conditions. Some keen and meticulous care can help you provide a healthy aquarium environment for the aquatic life inside it.

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