Saltwater Aquarium vs. Freshwater Aquarium: Making the Right Choice

saltwater aquarium vs freshwater aquarium

Fish are the most fascinating animals on the planet. There’s an amazing story around every corner in any body of water.

The ecosystems fish live in naturally, rivers, lakes and oceans, are split between saltwater and freshwater. An obvious difference in the water is salinity, or salt content.

When you’re considering a high-end custom aquarium in your space, you’re going to ask yourself, “do I want a saltwater aquarium or a freshwater aquarium?” 

Both are tremendously rewarding and entertaining. However, aside from the salt content in the aquarium water, they each offer very unique experiences! 


Other important elements that differ between saltwater aquariums and freshwater aquariums are the:


  • Design & Appearance
  • Equipment
  • Investment
  • Maintenance


Once you understand each of these elements, you’ll be able to make an informed decision about which aquarium is right for you.


In this article, I’ll give you all the info you’ll need to choose a saltwater vs. freshwater aquarium.


Let’s dive in! 


4 Main Differences in Saltwater vs Freshwater Aquariums


As I mentioned, the two aquarium environments each have their own distinct characteristics. 


In fact, you might even be wondering:


Why can’t saltwater fish live in freshwater? (or vice versa)


In the wild, there are actually some fish that are capable of moving from saltwater to freshwater during breeding cycles. These types of fish are categorized as anadromous, while the term catadromous refers to fish that migrate the opposite way, from freshwater to saltwater, to breed. 


In the aquarium trade, the vast majority of fish available can only survive in one or the other type of water. 


I’m going to get a little scientific here, but saltwater-only fish are unable to survive in freshwater because they cannot regulate the salt in the cells of their body. Osmosis would allow too much water to enter the body of a saltwater-only fish on a cellular level,  causing an internal imbalance resulting in catastrophe.


The opposite is true for most freshwater fish. If they were placed in saltwater, too much water would be removed from their bodies causing dehydration resulting in damage to their vital organs.


For your custom fish tank, you’ll need to choose between a saltwater aquarium setup or freshwater aquarium setup very early on in the process.


Here’s what to take into consideration.


1. Aquarium Design & Appearance


The first thing to consider when choosing a saltwater aquarium vs. freshwater aquarium is the way it will look in your space. 


You want it to blend seamlessly into the surroundings in your home or office.


Either type of aquarium will give you the “wow” factor you are looking for but some aquarium designs will blend better with your interior design theme than others. 


You’re probably already familiar with interior design themes (even though you may not know it). Some examples include: contemporary farmhouse, ultra-sleek minimalist, mid-century modern, industrial…the list goes on.

Your fish tank can reflect the same style, so that it enhances and compliments the overall feel.

Which style do you think fits your space best?

Freshwater Aquarium Design

A freshwater aquarium will usually have more earthy tones like browns and greens, using stone, wood and plants as the decorative elements. 

In this type of tank, the fish will add splashes of color and movement but the overall feeling is very tranquil and natural. It gives a very “Zen” feel.

The earthy tones of a planted freshwater aquarium are versatile and can add balance to a minimalist, modern or industrial interior design by bringing a natural, woodland feel into an otherwise “manufactured” space.

The cabinetry and glass-box design will make the greatest difference here. Choosing the right finish for the support structure as well as the right design for the tank itself will be key in making the freshwater aquarium blend into your space.

The best looking freshwater tanks usually have one or two showcase fish and maybe one or two schools of smaller fish. 

Some examples of showcase fish for freshwater aquariums are:

  • Angelfish
  • Discus
  • African cichlids

Let’s look at how each one might be right for your custom aquarium.

Freshwater Aquarium Fish


Native to South America, there are only 3 naturally occurring species of angelfish. However, they have been cross-bred by aquarium hobbyists for decades to create interesting color morphs that wouldn’t occur naturally. 

Angelfish are one of the best freshwater aquarium fish as they rarely become aggressive with smaller fish in the tank – even though they can be pretty feisty with each other!


Keeping Discus is considered, amongst veteran hobbyists, to be the pinnacle of the freshwater aquarium hobby. Until recent changes in breeding techniques, the water requirements for keeping Discus healthy were very challenging to maintain. 

More recently, Discus breeders have been able to breed Discus that are much easier to keep in a freshwater tank.

Discus like really warm water compared to other tropical fish. Heating the aquarium to 84-86º F degrees, compared to 75-80º F for most other tropical fish, seems to be one of the keys to keeping them happy and thriving. 

Breeders have also managed to breed fish with an amazing array of colors, which makes them a highly sought-after freshwater aquarium fish. 

Discus are on the higher end of freshwater fish-keeping, usually being sold in the range of $75 – $300 dollars. 

Definitely a status symbol, if you’re looking for that!

African cichlids

While there are dozens of species of African cichlids, the most common are the Mbuna species from Lake Malawi. There are several different color varieties of Mbuna and, when combined together, they can make a vibrant and active display. 

Mbunas are very aggressive, however their natural habitat provides limited space for nesting so they tend to live in very close proximity to one another. This allows for a “packed” aquarium look that will add stunning color to your living space. 

Always remember, the showcase fish will be the STARS of your freshwater aquarium. So choose wisely – or just ask your custom aquarium designer what they recommend.

Along with your showcase fish above, you’ll want to include one or two schools of fish in a freshwater aquarium.

The best freshwater schooling fish include:

  • Candy cane tetras
  • Neon or Cardinal tetras
  • Pentazona barbs
  • Cherry barbs
  • Zebra Danios

These schooling fish are the supporting cast in your freshwater aquarium design.

Freshwater Aquarium Plants

Using natural decorations, like wood, stone and live plants, creates a very calming visual.

Freshwater aquarium plants are typically shades of green or brown but there are a few that are red too.There are several variations in the shapes of the leaves, and even the patterns of color on the leaves. 

Saltwater Aquarium Design

A saltwater aquarium design is much more vibrant and energetic – it contains the full spectrum of spectacular colors. 

If you want color on color, this is it!

You’re probably much more familiar with the fish in a saltwater aquarium because of nature shows or public aquariums.

Saltwater fish generally have more bold colors and patterns. Corals will also contribute to the vibrance. 

Saltwater aquarium fish also tend to be more active. They’re constantly searching for food in order to fuel their bodies as they fight strong currents and compete with their tank mates.

If you’re looking for a lot of movement in your tank, a saltwater aquarium vs freshwater aquarium is the way to go.

In addition, reef aquariums looks amazing in modern interiors. Imagine a splash of color in a minimal space. It’s the perfect piece of living art that draws attention.

Let’s look at popular examples of showcase fish for a saltwater aquarium setup:

  • Clownfish
  • Tangs
  • Wrasses
  • Angels
  • Black Capped Basslet


Everybody loves Nemo! Your children will immediately find interest in your saltwater aquarium if they see something recognizable inside it. 

Ocellaris clownfish are relatively peaceful fish and their orange color is brilliant. 

The clownfish cousin, the pink skunk clownfish is also another great option. They are very peaceful as well and rarely bother any of their saltwater tank mates. 

Clownfish will also use anemones for shelter and watching them interact with the coral is quite amazing!


These are fish whose main diet consists of algae. There are several different species. Many are very common and easy to find. 

Yellow Tangs, Purple Tangs, and Desjardini Tangs are all from the genus Zebrasoma. 

These saltwater fish types are voracious algae eaters and their colors are breathtaking! 

The character Dory from the movie “Finding Nemo” is also a tang. The scientific name is Paracanthurus hepatus but they are commonly called Hippo Tangs or Regal Tangs.


Wrasses are another large family of saltwater fish that contains several peaceful and very colorful fish. 

It includes fish such as:

  • Melanurus wrasse
  • 6-line wrasse
  • McCosker’s wrasse

Some wrasses can be shy and reclusive but that can also be rewarding when you see the fish come out after a day or two hiding in your saltwater tank environment.


Saltwater angelfish are a diverse family of fish –  some of the most expensive and sought after fish in the industry. 

Most angelfish are not safe to keep in reef tanks due to their tendency to nip at corals.  

However, some people have success with them in larger reef tanks when their focus is spread out over a larger area (and they don’t continue to nip the same corals as frequently). 

Two pygmy angels have proven themselves safe – the Coral Beauty Angel and the Cherub angel. Both stay small with the Coral beauty getting to approximately 4-5”, while the Cherub Angel only grows to 2-3”.


This family of fish includes several different species. In general, they have bullet-shaped bodies and like to live in the cracks and crevices of the rock structure in reef tanks.

These fish are territorial and will fend off fish that try to encroach their space but they are otherwise peaceful, making them one of the best fish for a reef tank.

Basslets exist in a wide variety of colors and patterns. Some are purple, like the Black Capped Basslet and some are yellow like the Yellow Assessor Basslet. My favorite, the Carmabi Basslet ($$) is orange with pink stripes! 


Corals are incredible creatures! They’re part animal and part plant! The animal creates the structure and the color you see comes from algae that live within the tissue of the animal.

Some corals have a bony skeleton with a soft tissue covering, similar to human skin over bone. Other corals are composed completely of soft tissue. The soft corals will sway with the current while corals with hard skeletons don’t seem to move at all.

The algae that gives coral its color, lives in the soft tissue of the coral and uses sunlight for photosynthesis. Photosynthesis is the same process used by plants that grow on land to convert energy from the sun into food for the plant.

The food created by the algae is then used by the coral as energy for growth. 

Here are some examples of saltwater corals you can add to the landscape of your aquarium:

  • Forest Fire digitata
  • Favia Brains
  • Chalice Corals
  • Green Nepthea
  • Clove Polyp
  • Bubble tip anemone
  • Clams

2. Aquarium Equipment

Another big difference when comparing saltwater aquariums vs. freshwater aquariums is the amount of space you’re willing to dedicate to the aquarium filtration system and accessories. 

Freshwater Aquarium Equipment

A freshwater aquarium can typically be run using equipment that easily fits within the aquarium support stand. 

Canister filters are popular for freshwater aquariums because they are very effective and sit below the display area of the aquarium.

Even with extra equipment like CO2 systems and fertilizer dosing systems, a large freshwater fish tank will have plenty of room inside the support stand to house all of these items.

Saltwater Aquarium Equipment

Saltwater aquariums use large sump-style filters that require a large footprint. 

In addition, the following are all bulky additions:

  • calcium reactors
  • trace element dosers
  • protein skimmers
  • chillers 

It’s sometimes possible to fit them inside the support stand below the aquarium, but it often comes at the expense of easy access for maintenance tasks. 

Unless proper ventilation is used, chillers should never be placed inside a closed cabinet anyway. They need access to air circulation in order to function properly.
In the case of saltwater aquariums, it’s much more convenient to have the equipment in a separate room either below, or next to, the aquarium. This also allows for the inclusion of a proper tap water filter and a water storage container. The storage container will be used to house water for water changes as well as for topping off the system to account for evaporation.

3. Aquarium Investment

No matter what, owning a large-scale aquarium is a luxury.

However, the upfront cost of installing a saltwater aquarium vs. a freshwater aquarium certainly has differences. 

I’ll explain each one.

Freshwater Aquarium Cost

The main filtration component on any large, custom aquarium should be either a canister filter, a wet/dry filter or reef-sump. 

A lot of freshwater fish come from bodies of water that may stagnate and even have drastic shifts in clarity, temperature and purity. This means they have adapted to and are more tolerant of changes.

It also makes keeping them in aquariums a bit easier than saltwater fish. 

For this reason, we can use less complicated systems to filter freshwater aquariums than we can to filter saltwater aquariums. 

The filtration system is one of the largest expenses associated with the purchase of a custom aquarium so it is helpful to know which is best suited for your tank. 

Canister filters or wet/dry filters are the best filtration for a freshwater aquarium. The canister filter will likely be the less expensive option once the cost of installation is considered. 

Wet/dry filters may require time-consuming, custom plumbing in order to adapt them to the tank but canister filters can often be set up in a few minutes with the included accessories.

Saltwater Aquarium Cost

Saltwater fish are, generally, more sensitive than freshwater fish to shifts in water quality. So we tend to use more equipment and accessories in saltwater fish tanks. Those items will likely be more advanced, thus more expensive, than their freshwater counterparts. 

However, saltwater animals require greater dissolved oxygen levels to thrive compared to freshwater fish. For this reason, gallon-for-gallon, a saltwater aquarium will require a larger filter than the freshwater aquarium in order to maintain high oxygen levels in the tank. 

It should be noted that canister filters do not produce high levels of oxygen and should never be used as the primary source of filtration in saltwater aquariums. 

In addition, the saltwater aquarium filter system should have a protein skimmer incorporated into it. 

A protein skimmer oxygenates the water while also removing large amounts of organic material. This helps to maintain high water quality and prevents excessive algae growth. Protein skimmers are ineffective in freshwater because they depend on the density of saltwater to function properly.

4. Aquarium Maintenance

The final thing to consider is the long term activity of maintaining a saltwater aquarium vs. freshwater aquarium. 

At the base, the labor is roughly the same for each but the frequency and cost of supplies is different.

For instance, both types of aquariums will get algae growth on the glass. In a freshwater fish tank, the algae may take up to a week to show whereas on a saltwater fish tank, the algae will appear around day 2 or 3. 

This is why I recommend weekly service visits for saltwater aquariums and bi-weekly service visits for freshwater aquariums. 

Additionally, reef tanks will need water changes either every week, or every 2 weeks, depending on the amount of fish and coral in the tank, to maintain good water quality and nutrient levels for the corals. 

Freshwater tanks will need water changes every 2 to 4 weeks to reduce waste buildup and algae growth as much as possible.

There are also additional material costs for the saltwater setup. 

The most obvious is salt. When servicing a saltwater aquarium, we mix dry marine salt into filtered tap water to create saltwater. Marine salt can range anywhere from about $0.25/gallon to about $0.75/gallon. 

You’ll also have to add the cost of pre-filtering your tap water or purchasing filtered water. There will be other differences as well such as use of higher grade filter media for better water quality. These can effectively be double the cost of the freshwater versions. 

Whether you choose a freshwater aquarium or a saltwater aquarium for your home, it’s important to have the right professionals servicing your tank.


Deciding what type of custom aquarium design to get can feel overwhelming when you don’t have all of the necessary information. 

Now that you know the most common differences between a saltwater aquarium vs freshwater aquarium, you’ll be better prepared to make the right choice when it comes to these things:

  • Aquarium Design & Appearance
  • Aquarium Equipment
  • Aquarium Investment
  • Aquarium Maintenance

Which do you think you’ll choose – a saltwater aquarium or a freshwater aquarium?

Let me know in the comments below! 

From deciding what style of aquarium you want in your space, to design and then installation, you’ll want the most knowledgeable experts by your side. Diamond Aquatics is here to guide you on your way to the custom aquarium of your dreams and to provide top-notch aquarium maintenance service to keep your fish tank looking its best. 


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  1. Very informative ..well written. We have a 75 gal Iasian community and a 190 gal Tanganyika biotope complete with sun rise, sun set, and water changes are Sunday so we have a lightning storm that day .
    Perfect hobby .thanks for safe

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