From Freshwater To Saltwater - Find Out What It Takes

Categories: Maintenance, Additives & Water Chemistry, Guides & How-Tos

Last updated: Jan 17, 2022

Freshwater Rainbowfish and Saltwater Dwarf Angelfish

Keeping a saltwater aquarium really is not all that much different from keeping a freshwater aquarium. While saltwater tanks often get a bad rap for being "difficult & expensive", they really are not any more demanding than a freshwater aquarium and can be just as affordable too. Making the switch from a freshwater to a saltwater aquarium not only offers a whole new world of livestock, but you also get to experience the saltwater and reef aquarium community through connecting with other hobbyists who share the same passions and interests as you.

Most aquarists start off keeping freshwater aquariums. When the day comes you are ready to build a saltwater tank, you have already gathered much of the skills and equipment necessary to build your very first saltwater tank. This alone makes the process incredibly easy and the fact remains, there really isn't a big difference between the two. So let's dissect the process and find out what it takes to transition from a freshwater aquarium to a saltwater aquarium.

What's The Difference?

The answer can be found within a simple definition of each. The very foundation of what makes a freshwater and saltwater aquarium different is the water and animals inside.

Freshwater Aquarium: An aquarium that contains fresh water and houses plants and animals from freshwater ecosystems.
Saltwater Aquarium: An aquarium that contains salt water and houses corals and animals from marine ecosystems.

This is just the highest level of classification of aquarium types, within each you have a variety of disciplines and specialty tanks to explore which are defined by what you choose to keep inside the tank. For example, a "Cichlid Tank" and "Planted Tank" are both types of freshwater aquariums. A "FOWLR - Fish Only With Live Rock" and "Reef Tank" are both types of saltwater aquariums.

As an aquarist, you will be exposed to and learn about these different tank types, all of which have specific care requirements unique to the animals inside. In fact, that's one of the best parts of the aquarium hobby is the chance to constantly grow and challenge yourself as a hobbyist with new pets and tanks. Regardless of your goals or what you have already achieved, ALL AQUARIUMS, both freshwater and salt, are built upon the same basic principles and techniques.

Step #1 - The Water

Freshwater aquariums are filled with fresh water from your tap. It is best to use filtered RO water, but you can also just use a simple water conditioner to eliminate chlorine and ammonia. In a saltwater aquarium, you start with that very same filtered or conditioned freshwater, but you must also add synthetic sea salt or "salt mix" in order to make it saltwater. The salt mix contains everything found in natural seawater outside of H2O.

This is going to be the primary difference and the most critical. Saltwater fish and invertebrates require saltwater to survive. Freshwater plants, fish, and invertebrates require fresh water to survive. So long as you can wrap your head around that, just about everything else is the same between a freshwater and saltwater tank, including the setup process, equipment, and maintenance.

Step #2 - Equipment

This is something that confuses many folks just because saltwater does have a tendency to wear down equipment faster than freshwater. A majority of the equipment used on freshwater tanks is safe for use on a saltwater aquarium. That means the aquarium, filters, heaters, and pumps you already have can be used to build a saltwater tank. Just be sure to give the equipment a thorough cleaning in between setting up tanks.

Aquariums - All glass or acrylic tanks designed to hold water are safe for either freshwater or saltwater.
Filters - Most power hang-on filters, canister filters, wet-dry filters, and sumps are safe for both fresh water and saltwater aquariums. That said, most all metals will rust in saltwater so you want to stay away from metal pipes, fittings, and components. Titanium is really the only metal used inside a saltwater tank; everything else is made of glass, ceramic, plastic, or some other non-metallic material.
Heaters - Glass, titanium, and plastic aquarium heaters are safe in both freshwater and saltwater tanks. Stainless Steel heaters are not safe for saltwater tanks.
Pumps - While some pumps are not rated for use in a saltwater tank (because of metal parts and seals), most companies advertise this suitability right on the package. All of the pumps we stock here at BRS are safe for use in both freshwater and saltwater aquariums but if you are just not sure, ask the manufacturer or give us a call.
Lighting - Freshwater and saltwater tanks usually have different colored lighting. This is most important with planted aquariums and reef tanks that contain photosynthetic plants or corals. If you are keeping only fish in your tank, the color and intensity of the light are far less critical.

Step #3 - Substrate

This is an area where things are different between the two types of tanks. Most freshwater tanks will have gravel on the bottom with artificial decor, rocks, and/or driftwood to create the hardscape. Not only does this more closely match the environment these freshwater animals encounter naturally, but the materials used in freshwater decor and substrates are often not safe for use in a saltwater tank.

In a saltwater tank, you will be using crushed coral or aragonite-based sand across the bottom and calcium carbonate-based "live rock" to fill in the aquascape. It's almost always specifically marketed for saltwater aquariums and will create a more natural environment for marine animals. Some artificial decorations and fake plants are safe for use in both saltwater and freshwater tanks, but many are not. Defer to the manufacturer's recommendations and if you are not sure, don't risk it.

Step #3- Cycling and Beneficial Bacteria

The bacteria that exist in freshwater play the same role it does in a saltwater tank, but the bacteria are unique based on the type of water. While both types of tanks must harbor a successful nitrogen cycle and support beneficial bacteria, the specific bacteria that live in a freshwater tank are different than those that grow in a saltwater tank.

For this reason, you must cycle a saltwater aquarium with saltwater and you must cycle a freshwater aquarium with fresh water. This way the appropriate beneficial bacteria will grow to support the nitrogen cycle. If you already have a freshwater tank, it must be emptied and cycled with new saltwater before adding any marine animals are added.

Step #4 - Maintenance

Maintenance requirements are pretty much the same no matter what kind of aquarium you have. You feed the fish, clean the glass, maintain the filters, and do water changes. These requirements remain just as important in both freshwater and saltwater aquaria. Really the only difference here is you are going to be mixing up saltwater to use in your tank before water changes.

Learn How To Mix Saltwater with BRStv

Step #5 - Livestock

Of course, the livestock you keep is going to vary wildly and there will be specific requirements that come with those different animals. This holds true for both freshwater and saltwater aquariums so the advice really is the same. You should be using the right kind of food, provide the right water parameters and environmental conditions based on the type of fish and animals you choose to keep. Tailoring the environment specifically for the animals in your care is always of utmost importance for long-term success in an aquarium.

This includes the wellness and compatibility of the animals too. You must choose healthy animals that will be able to survive alongside each other in the aquarium. Disease and aggression are common threats in any aquarium, freshwater or salt.