Freshwater Aquarium vs. Saltwater Aquarium

Updated August 12, 2019
Author: Mike - FishLore Admin
Social Media: FishLore on Social Media

Are you thinking about converting that freshwater aquarium into a saltwater aquarium? We'll shed some light on some of the differences in the setup of a freshwater vs. saltwater aquarium.

There are many differences when it comes to freshwater aquariums versus saltwater aquariums. These setups can be quite different when it comes to initial and ongoing costs, everyday chores and maintenance tasks and care requirements for the fish and inverts.

This article was written for those aquarium hobbyists interested in the main differences in keeping a saltwater tank versus a freshwater aquarium. Let's get started.

Tank types

In the freshwater world you hear people talking about African Cichlid and New World Cichlid tanks, brackish tanks, planted tanks, predator tanks, etc. Well, the saltwater side of the hobby has some different types of tank setups as well. There are the Fish-Only tanks, FOWLR tanks (Fish Only with Live Rock) and Reef Tanks.

These three saltwater aquarium types progress in startup and maintenance costs. Fish-Only tanks can be considered on the low end for startup costs while FOWLR tanks are moderatly priced and reef tanks could be considered high priced. Refugiums for saltwater aquariums are gaining steam these days as many hobbyists realize the important benefits these refugiums can provide.

Aquarium setup costs

Let's start with the initial setup costs for starting these two aquarium types. To keep it simple, we'll lookup at fish-only systems, except for the reef tank which is for corals and invertebrates. For a freshwater aquarium you may have the following initial equipment list. Please keep in mind that these are very rough estimates on prices and we used a 29 gallon aquarium for this example. *June 2007 - Added the approximate total cost for setting up a Saltwater Reef Tank.

Freshwater Aquarium 29 Gallon Tank
Gravel (substrate)$20
Filter (power filter)$50
Aquarium Light (LED or regular fluorescent)$50
Test kits (pH, ammonia, nitrite, nitrate)$50
Food, Nets, Scrapers and other equipment$25
Quarantine Tank$25
Approximate Total Cost:$270

Saltwater Aquarium 29 Gallon Tank
Sand (substrate)$50
Powerheads for water movement$50
Protein Skimmer$150
Salt Mix$30
Live Rock$100
Test kits (pH, ammonia, Nitrite, nitrate, calcium, alkalinity)$70
Lights (LED or regular fluorescent)$50
Food, Nets, Scrapers, similar$25
Quarantine Tank$25
Approximate Total Cost:$635

Reef Tank 29 Gallon Tank
Sand (substrate)$50
Filter (though not really necessary)$25
Powerheads for water movement$75
Protein Skimmer$150
Hydrometer or even better a Refractometer$15
Salt Mix$30
Live Rock$100
Test kits (pH, ammonia, Nitrite, nitrate, calcium, alkalinity, phosphate)$90
Lights (LED, T5HO, Metal Halide or better)$250
Food, Nets, Scrapers, similar$25
Refugium for culturing live foods for corals and fish$150
Quarantine Tank$25
Reverse Osmosis Filter Unit$200
Approximate Total Cost:$1275

As you can see, a saltwater aquarium requires some additional aquarium test kits and some additional equipment not found on the freshwater side of the hobby. You'll need to invest in a good quality protein skimmer and some good quality live rock. Live rock is important from a biological filter perspective and if you're using live rock you don't have to use an external filter on the tank. Let the protein skimmer remove the dissolved wastes. The external mechanical aquarium filter may actually become a source of nitrates if not cleaned often enough since the power filter just traps waste. The protein skimmer on the other hand actually removes the dissolved organics from the water.

Quick note on live rock

I wouldn't recommend that a newbie start a saltwater tank without live rock. There are just too many benefits to having it in your marine aquarium. It's a great biological filter, provides food for various species, provides hiding places and homes for others and it looks great. There are other benefits too. Check out the article on saltwater live rock for more information. Setting up and keeping a marine fish tank stable without live rock can be more difficult than starting one with ample quantities of good quality live rock.

Water changes are easier for freshwater tanks

The periodic partial water changes are one of the most important tasks that a hobbyist performs on a regular basis and the process is a little different when you move into saltwater aquariums. Freshwater aquarists generally can remove some of the tank water (say 10%) with an aquarium vacuum and then refill the tank with dechlorinated tap or filtered water and your tank could stay in a great shape if you do this regularly. Saltwater hobbyists can't use the same vacuum (python) do this since the saltwater has to be mixed up days before hand in a separate container. You can use a bucket to mix new saltwater or if you have a bigger tank, a larger holding container can be used.

Saltwater fish are generally more expensive than freshwater fish

Cruise through the aisles at any saltwater fish store and your jaw might drop when you notice the price tags on some of the saltwater species. With the exception of some of the really common species such as green chromis and other small damselfish, most fish are $15 or higher. Saltwater invertebrates also come with really high price tags, especially for those hobbyists not living near coastal areas. Shipping and handling will get added to the price tag.

Quarantine all new fish!

Most marine species come from the reef and will need to be quarantined before introducing to your main tank. You don't have to go all out here. A simple bare bones quarantine tank setup will be fine. Many freshwater species are farm raised since they are (in general) easier to breed than their saltwater counterparts. Clownfish, dottybacks, dwarf angelfish and some other saltwater species are now being aqua-cultured (farm raised) but their price tags are even more expensive since they are usually hardier than those caught in the ocean. The farm raised species are worth it! We also need to support these breeders so that more species can be raised going forward. Since most saltwater species are coming direct from the wild, they may be carrying various internal or external parasites or diseases.

Lots of invertebrates to choose from

There seems to be an unlimited amount of invertebrates available to keep in a saltwater tank. Freshwater hobbyists certainly have invertebrates available but not to the extent of saltwater. You name it, a local fish store around you probably has it. From corals, clams, shrimps, worms, sea stars, feather dusters, etc. The amount of saltwater invertebrates available to hobbyists is vast and it seems to be growing all the time.

Saltwater fish colors are amazing

While there are some exceptionally colorful freshwater species (bettas, neon tetras, discus, etc) there are many more saltwater species that are truly breathtaking to view. You've never seen the color yellow until you've seen a school of healthy yellow tangs swimming in a large aquarium or on the reef!

Getting saltwater fish eating can sometimes be challenging

This goes back to most of the species being wild caught. Freshwater species may be second, third, fourth, or Nth generation or more from a fish farm and they are given flakes or other man-made fish preparations. Getting freshwater fish to eat should pose no problems for even the novice aquarist. Saltwater fish on the other hand are from the wild (generally speaking here) and may need to be slowly weaned onto standard aquarium foods over a period of several weeks or months. Specialized diets become even more important with saltwater fish species, since inadequate diets can lead to stress, which can lead to lowered immune systems and disease causing us to lose our $75 saltwater fish!


In general, keeping saltwater fish is more expensive and more difficult than keeping freshwater fish. However, once established they do seem to be less demanding and water quality tends to stay better in tanks using live rock. Live plants perform similar (albeit to a lower degree) functions in water filtration in a freshwater aquarium. If you've been keeping freshwater fish tanks for some time now successfully the switch to a saltwater aquarium should not be all that difficult. If you have the desire, the fortitude to do the necessary research before acquiring animals and aquarium equipment and the money necessary to run a saltwater aquarium, then by all means go for it! Once you get started you'll be wondering why it took you so long to get into the saltwater side of the hobby.

Happy Fish Keeping!

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