Can You Use Ocean Water For Saltwater Tanks?

Using ocean water for your saltwater tank might be an option for you.

If you have the advantage of living near the ocean it’s something you may want to consider. 

But there are challenges with using ocean water that might prevent you from using it. 

Like most things, there are pros and cons.

In this article, I will explain everything you need to know about using ocean water in your saltwater tank so you can decide if it’s a good option for you.

Can you use ocean water in a saltwater tank?

Yes, you sure can. Ocean water can be a very effective and affordable way to have natural saltwater for your tank. 

When setting up a saltwater tank you will have 2 options to decide on for water.

  1. Ocean water – Natural seawater (NSW)
  2. Make your own saltwater mix – Artificial saltwater (ASW)

Both of these are viable options but if you don’t live close to the ocean, then making your own saltwater will be the only way to go.

Natural seawater can be a free option for getting saltwater into your tank. But using it comes with challenges that you need to be aware of. 

First, you need to find a good source of clean water. Ensure that the area you want to take water from is free from pollution.

Stay away from areas that have boats, cars, industrial waste, and other pollutants that will be harmful to your tank.

Beaches, harbors, and bays can be a bad option as these areas generally have poor water due to pollutants. Most times you can tell if the water quality is poor just by looking at it. 

Avoid these areas

The best areas to collect natural seawater is well offshore where there is current.

Stay away from river inlets and mouths, beaches, and marshes.

If you don’t have a boat or another option to get water that is offshore, you can still collect close to the shore just be cautious of areas of pollution and pick a time when it is high tide.

Avoid areas where there is freshwater mixing and check the water salinity level to ensure it is safe to use. 

Another challenge of using ocean water is you will need equipment to collect it.

Depending on your tank size and the amount of water you are looking to collect, you may need to have several buckets or containers with tight-fitting lids to transport the water.

If you are getting a very large amount, you may need to use a water pump with tubing to fill your containers.

It’s also important to pump the water through a filter sock to collect any debris and pests that might be in the water. 

You will also need to perform water tests to make sure there is no chlorine and that all other water parameters are within normal limits for aquarium use.

Here are some advantages and disadvantages of using natural seawater.


  • Water is free
  • Contains beneficial microorganisms like phytoplankton
  • No need to purchase salt
  • Faster than making rodi water and mixing saltwater


  • Can be a lot of work and manual labor
  • Possible harmful pollutants
  • Requires filtering
  • Large amounts will need proper storage
  • More testing required

Another thing to consider if using ocean water is you need to store it in a proper place if not using it right away. You will need a cool, dark place as light may cause algae growth in the water. 

There may be someone in your local area that offers water delivery for a fee. They may have all the equipment needed and can easily collect ocean water and deliver it to you. 

Taking everything into consideration, decide on whether using natural seawater is the right option for you.


How to make ocean water safe to use

Once you bring the ocean water home, there are a few more steps to make it safe to use in your tank. 

If you filtered the collected water through a sock, most of the parasites and debris would have been filtered out. But there still may be spores and other life that could still be there.

You can eliminate that by using chlorine. It is important to use chlorine properly and don’t overdo it. This includes aerating the water for a period of time and letting it sit as the chlorine will dissipate.

You can also use a dechlorinator like prime before using the water in your tank.

Before using the water, you will need to heat it to the proper temperature of your tank. Ocean water will most likely be cold depending on where you collect it. 

Is it legal to take ocean water?

I don’t believe there are any laws that would prevent you from taking ocean water. If you are taking ocean life such as fish, corals, invertebrates, you may have legal concerns.

It’s always best to check with your local authorities ahead of time to check the current laws. Depending on where you live there could be a ban or specific rules and regulations to follow regarding the collection of ocean water.


If you live near an area where it would be easy to collect ocean water for your saltwater tank, you might want to consider it. There are advantages to doing so.

Many people love using natural seawater and providing the water is clean and clear, you should have no problems using it.

Your corals and fish will love you for it!


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