Saltwater vs. Freshwater 75-Gallon Fish Tanks

One important consideration for a large fish tank is whether it will be a saltwater or freshwater setup. Both offer unique advantages and disadvantages, so the end choice must be left up to you. In that spirit, this guide will aim to simply provide information, rather than to sway you in one direction.

Types of Freshwater and Saltwater Tanks

When deciding exactly what you’re wanting from your fish tank setup, it’s important to keep in mind that “freshwater” and “saltwater” are just parent terms – there are several different categories of each water type.  It makes sense to choose your fish tank based on the exact sub-type you’re after, rather than limiting yourself to a specific category without giving further consideration to the end setup you desire.

This isn’t a comprehensive list, but some of the more popular sub-types of each tank include:


  • Tropical tanks
  • Coldwater tanks
  • Brackish tanks
  • Predator tanks


  • Fish-only tanks
  • FOWLR (Fish Only With Live Rock) tanks
  • Reef tanks

Each of these types presents its own aesthetic advantages, along with unique setup costs and maintenance requirements.

Considering Fish Types

Of course, the most important difference between freshwater and saltwater is the type of fish your tank can support. Very few creatures are able to survive in both types of water, so your choices will be limited depending on the type of fish you wish to keep.

When shopping for fish, you’ll quickly notice a price difference between the two categories. Saltwater fish tend to be substantially more expensive than their freshwater cousins. However, these fish can be much more exotic in terms of both rarity and appearance, with saltwater fish typically boasting vibrant, unique colors.

The more popular freshwater fish are Goldfish, Betta fish, Tetras, Gouramis, and the Chichild. On the other side of the spectrum, saltwater tank owners will usually opt for Clownfish, Butterflyfish, Blennies, or Dottyback fish. There are many other options besides these common choices, of course, and there are additional choices that are much rarer and exotic than these options – especially when it comes to saltwater fish.


Any fish tank is going to require a degree of maintenance, especially when the large 75-gallon setups are your goal. As a rule of thumb, saltwater tanks are going to require more work and closer attention to detail when making chemical adjustments. With that said, the results can be well worth the small amount of additional upkeep needed to maintain a saltwater tank.

As the name implies, a saltwater tank will require you adding the ideal amount of salt to achieve a healthy salinity for your fish. However, salt in this ratio doesn’t simply dissolve, so you’ll have to stir it continuously until the salt is fully dissolved.

This presents the largest degree of effort when you first set up and fill your tank, but it will also require some extra work each time you do a partial flush or top off the water level. For convenience purposes, most saltwater tank owners keep a batch of saltwater mixed up for topping off the levels on the fly.

You can buy premixed saltwater, but the cost is much higher than simply mixing it yourself. Measuring might work initially, but as the water evaporates and leaves salt behind, you won’t be able to maintain the ideal salinity without some additional tools – namely a hydrometer. Using a hydrometer will allow you to accurately gauge the water salinity at any given point in time.

Both types of tank will require additional chemical maintenance, such as additives to remove chlorine and other chemicals from any tap water that’s added to the tank.


One fairly obvious advantage of a saltwater tank is the ability to sustain coral. Having your own reef can provide something interesting to watch grow and develop in addition to your fish. If that’s of importance to you, then the obvious choice is a saltwater tank.

The presence of coral itself presents another host of challenges, including further maintenance of ideal lighting, diet sources, and water conditions – all of which coral needs in order to thrive.

Equipment Differences

In line with the theme of increased complexity for a saltwater setup, it’s no surprise that the equipment demands can also be more complex. In addition to a hydrometer to measure salinity, you’ll need to keep test kits to maintain ideal levels of alkalinity and calcium. Saltwater fish tanks will also usually need powerheads, a sump system, and a protein skimmer to keep the water ideal.

Making the Decision

To summarize all of these points, saltwater fish tanks can provide a beautiful aquarium experience home to more exotic specimen than a freshwater tank could support. With extended possibilities, like coral reefs, you’ll have plenty of room to grow and adapt. On the downside, the initial equipment cost and the increased expense of the actual fish make this suitable for those on a higher budget.

Only you can decide which option is right for you. If you’re willing to spend a bit more money and effort, a saltwater setup can provide years of enjoyment. If you’re wanting a more basic setup that suits a lower budget, then a freshwater tank might be the right call.


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