Convert a Freshwater Aquarium to Saltwater Aquarium

Photo of author
Written By Esrat Jahan

Esrat is a well-regarded animal rescue expert and writer with nearly a decade of experience in animal advocacy. Esrat is the former editor of Tails Pet Magazine and volunteers in animal rescue, including Chicago’s Anti-Cruelty Society and Starfish Animal Rescue.

To convert a freshwater aquarium to a saltwater aquarium, thoroughly clean and refurbish the fish tank, as saltwater fish and plants cannot survive in a freshwater setup. It is important to note that freshwater aquatic creatures cannot live in a saltwater tank.

However, the same tank can be used as long as the system type is changed.

Convert a Freshwater Aquarium to Saltwater Aquarium


Steps To Convert A Freshwater Aquarium To A Saltwater Aquarium

Converting a freshwater aquarium into a saltwater aquarium may seem like a daunting task, but with the right steps and proper preparation, it can be a smooth and successful process. Whether you want to explore the vibrant world of saltwater fish or create your own mini coral reef, this guide will take you through the necessary steps to make the conversion. Let’s dive in!

Remove The Fish

The first step in converting your freshwater aquarium to a saltwater aquarium is to remove all the fish and other aquatic creatures living in the tank. It’s essential to give them a suitable temporary home during the conversion process to ensure their safety and well-being.


  • Prepare buckets or containers with adequate water and oxygen supply for each fish.
  • Handle the fish gently and avoid causing stress or harm during the transfer.
  • Make sure to keep the water at a stable temperature and provide suitable hiding places for the fish in their temporary homes.

Drain And Clean The Tank

After safely removing the fish, the next step is to drain and clean the tank to eliminate any traces of the previous freshwater environment. This ensures a fresh start for your new saltwater setup.


  1. Unplug any electronic devices connected to the tank and remove decorations, rocks, and plants.
  2. Using a siphon or a gravel vacuum, drain the water from the tank while also removing any debris or waste present.
  3. Tip: Dispose of the old water safely and avoid contaminating other water sources.
  4. With the tank empty, carefully clean all surfaces, including the walls, gravel, and equipment, using an aquarium-safe cleaning solution.
  5. Rinse everything thoroughly with fresh water to remove any cleaning residues before refilling the tank.

Switch The Lighting

The type of lighting required for a saltwater aquarium differs from that of a freshwater tank. Saltwater tanks often require stronger lighting to support the growth of marine plants and corals. Therefore, switching the lighting is an essential step in converting your aquarium.


  1. Remove the existing lighting fixture from the tank, ensuring to disconnect it safely from the power source.
  2. Install a suitable lighting system specifically designed for saltwater aquariums. Consider factors like the intensity and spectrum of light required for your desired marine life.
  3. Tip: LED lights are a popular choice due to their energy efficiency and ability to provide customizable lighting options.
  4. Position the new lighting system above the tank, using mounting brackets or other appropriate fixtures.
  5. Connect the lighting system to a timer to ensure a consistent lighting schedule for your saltwater aquarium.

Add Base Sand

In a saltwater aquarium, a layer of base sand is crucial for creating a stable and natural substrate for your marine life. This sand provides a suitable environment for beneficial bacteria and can also act as a home for many bottom-dwelling organisms.


  1. Choose a high-quality marine-grade sand suitable for your desired aquarium setup.
  2. Carefully pour the sand into the empty tank, ensuring to create a smooth and even layer.
  3. Tip: You can use a piece of cardboard or a plastic plate to distribute the sand evenly and prevent it from clouding the water.
  4. Level the sand layer using your hand or a tool, making sure it is uniformly distributed across the tank’s surface.
  5. Rinse the sand with saltwater multiple times to remove any impurities or dust.

Upgrade Mechanical Filters

Switching from a freshwater to a saltwater aquarium often requires upgrading the mechanical filtration system. Saltwater tanks demand more efficient filtration due to the higher levels of waste produced by marine creatures.


  1. Assess the capacity and effectiveness of your existing filter system.
  2. Research and invest in a suitable protein skimmer, which helps remove organic compounds and dissolved organic matter from the water.
  3. Tip: Consider a sump system, which can provide additional space for filtration equipment and increase water volume in the aquarium.
  4. Install the upgraded filtration system following the manufacturer’s instructions and ensure it is appropriately sized for your tank.
  5. Monitor the filtration system regularly and perform necessary maintenance tasks, such as cleaning and replacing filter media, to maintain optimal water quality.

With these steps completed, you are well on your way to converting your freshwater aquarium into a thriving saltwater haven. Take your time, pay attention to detail, and always prioritize the well-being of your aquatic inhabitants. Enjoy the excitement of building and maintaining your own piece of the ocean in the comfort of your home!

Convert a Freshwater Aquarium to Saltwater Aquarium


Considerations And Challenges

Converting a freshwater aquarium to a saltwater aquarium poses various considerations and challenges. It involves switching the system type and ensuring proper equipment, such as a protein skimmer, is used for marine water. Additionally, thorough cleaning and refurbishing of the tank are necessary to provide a suitable habitat for saltwater fish and plants.

Can You Use The Same Tank?

Yes, you can use the same tank if you want to convert it from a freshwater aquarium to a saltwater aquarium. The aquariums themselves are not specifically designed for use as either a freshwater or saltwater tank. However, it’s important to note that freshwater aquatic creatures cannot live in a saltwater setup. So if you’re planning to switch to saltwater, you’ll need to remove all the freshwater fish and plants from the tank first.

Preparing The Tank For Saltwater Species

Once you have removed the freshwater fish and plants from the tank, the next step is to thoroughly clean and refurbish the tank to make it suitable for saltwater species. This involves cleaning the tank walls, gravel, and decorations to remove any traces of freshwater residue. It’s also important to rinse the tank thoroughly to remove any cleaning agents that could harm the saltwater species. To ensure the tank is ready for saltwater, you’ll also need to replace the substrate and add live rock and sand. Live rock is beneficial as it provides natural filtration and a habitat for beneficial bacteria and marine organisms. Adding sand helps create a natural environment for the saltwater species and can contribute to the overall aesthetics of the tank.

Maintenance And Cost Differences Between Freshwater And Saltwater Tanks

Maintaining a saltwater aquarium requires more effort and attention compared to a freshwater tank. The water parameters in a saltwater tank need to be carefully monitored and maintained, including salinity levels, pH levels, and temperature. You will also need to invest in equipment like protein skimmers, powerheads, and additional filtration systems to ensure the water quality is optimal for the saltwater species. In terms of cost, setting up and maintaining a saltwater aquarium can be more expensive compared to a freshwater tank. The saltwater species themselves tend to be more expensive, and the equipment required for a saltwater setup can be costlier too. Additionally, salt mixes and marine supplements are necessary to maintain the correct salinity and nutrient levels in the tank. Overall, converting a freshwater aquarium to a saltwater aquarium comes with its own set of considerations and challenges. While the process requires time, effort, and investment, it can be a rewarding experience for aquarium enthusiasts looking to explore the vibrant and diverse world of saltwater species.
Convert a Freshwater Aquarium to Saltwater Aquarium


Frequently Asked Questions Of Convert A Freshwater Aquarium To Saltwater Aquarium

Can I Turn My Freshwater Tank Into A Saltwater Tank?

Yes, you can turn your freshwater tank into a saltwater tank by cleaning and refurbishing it before adding saltwater aquatic creatures. Remember, saltwater fish and plants cannot survive in a freshwater tank. Freshwater tanks are easier to maintain and less expensive than saltwater environments.

Can You Put Saltwater Fish In A Freshwater Aquarium?

No, saltwater fish cannot survive in a freshwater aquarium. They require a specific saline environment to thrive.

Do Saltwater Tanks Need Special Filters?

Saltwater tanks do not require special filters. You can use the same filters as in a freshwater tank, except for a protein skimmer which is specific to marine aquaria. Freshwater filters can be used in marine or brackish water aquariums.

Is A Saltwater Tank Harder To Maintain Than A Freshwater Tank?

Maintaining a saltwater tank is generally more difficult than maintaining a freshwater tank. Saltwater tanks require more equipment, such as protein skimmers, and need more maintenance to maintain proper water parameters. Additionally, saltwater fish and plants are more sensitive and require specific care.


Converting a freshwater aquarium to a saltwater aquarium requires careful planning and consideration. By following expert tips and thoroughly cleaning and refurbishing the tank, you can successfully make the transition. Remember, saltwater fish and plants cannot survive in a freshwater setup, so it’s important to make the necessary changes.

While saltwater tanks may require more maintenance and be slightly more expensive, the beauty of a coral reef and the vibrant colors of saltwater fish make it a rewarding endeavor. So go ahead and take the plunge into the world of saltwater aquariums!

Leave a Comment