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What Saltwater Fish Can Live in a 5-Gallon Tank

Starting a Nano saltwater tank can be easier than you may think, provided you maintain it properly. A ‘Nano tank’ is any aquarium that holds less than 30 gallons of saltwater. If you are new to the aquarium hobby and wondering if and what you can keep in a 5-gallon saltwater tank, well, I have the answer for you below.

Small marine fish that are peaceful in nature and non-territorial can survive in a 5-gallon tank. The best options are angelfish, cardinalfish, gobies, and grammas. Other possibilities include clownfish and chromis fish, however, these two species can be aggressive. It’s important to note that when it comes to saltwater aquariums, bigger is better, regardless of the size or species of fish you keep.

Now that you know the best types of saltwater fish to keep in a nano tank, let’s take a closer look at this further and in more detail. I’ll explain how many saltwater fish can be kept in a 5-gallon tank, what other aquatic creatures can live a small saltwater aquarium and whether (or not) it’s difficult to maintain a Nano saltwater tank.

So, if you’re ready to learn more, then let’s get started…

How Many Saltwater Fish Can I Put in a Gallon?

The general ‘rule-of-thumb’ when it comes to keeping saltwater fish in an aquarium is 1.5 centimetres or ½ inch of fish per gallon of water. This is half of what the recommended amount is for freshwater fish, which means you cannot keep near as many saltwater fish in an aquarium as you can freshwater fish. However, this is just a guideline and can be modified depending on how well you maintain your tank.

Many variables affect the amount of fish you can keep in a saltwater aquarium. These include how effective your filtration system is, how many invertebrates/corals you have in the tank, and how well-established the tank is. If you’re willing to put in the time and effort needed to properly sustain your saltwater aquarium, then you can likely keep a bit more than recommended.

For a small nano tank like a 5-gallon version, most experienced hobbyists believe you should never stock it with more than 2.5 inches (or 6 centimetres) of fully-grown fish. Saltwater fish need ample space in an aquarium – not just to survive but to thrive. Overstocking a nano tank will not only make it harder to maintain, but it’ll also lessen the quality of life for its inhabitants.

Can You Have a 5 Gallon Saltwater Tank?

Yes, you can have a 5-gallon saltwater tank, but you must be careful how many and what type of fish you choose to keep. Many saltwater fish tend to be aggressive or territorial and can grow to be quite big. As well, saltwater fish often need large volumes of water like that of their natural habitat – which is the ocean, of course. Saltwater tanks also more in the way of maintenance than freshwater tanks.

Can Angelfish Live in a 5 Gallon Tank?

Dwarf pigmy coral beauty angelfish are a great addition to any nano tank. A passive reef fish, this species remains small and grows only to a few centimetres in length. For the most part, they are easy to care and fun to watch as they glide effortlessly through the water showcasing their bright, beautiful color patterns.

For a 5-gallon tank, it’s best to keep only 2 dwarf angelfish so they have enough room in the aquarium to swim freely. While they enjoy the company of other angelfish, they tend to fight with each other if they don’t have adequate space to move about. They can also get nippy with the smaller fish in the tank. Therefore, if you decide to keep angelfish in a tiny Nano tank, then keep only angelfish.

Can a Clownfish Live in a 5 Gallon Tank?

Clownfish can live in a 5-gallon tank, provided you only keep 1 or 2. Often aggressive and territorial in nature, what these small fish lack in size they make-up for in temperament! While you can keep just 1, they prefer to be kept in pairs and like to swim together. They have an innate ability to breed which is why any more than 2 will lead to an overcrowding of the tank in no time.

The orange or true percula clownfish is one of the smallest species and would make a nice addition to a 5-gallon Nano tank. Under no circumstances should you keep a clownfish (or any saltwater fish – in my opinion – no matter how tiny) in any tank with less than 5 gallons of water. Keep in mind that natural habitat for these fish in the ocean near coral reefs where they have ample room to swim and explore.

Can Gobies Live in a 5 Gallon Tank?

Gobies are an excellent choice for a small Nano tank. They remain small even as adults and therefore can survive in a 5-gallon saltwater aquarium. The neon gobby, for example, not only swims about gracefully displaying its glow-in-the-dark color patterns, but it also helps keep the tank clean. Hence why they’re often referred to as ‘cleaner’ or ‘perching’ fish.

Other species of goby fish that can live in a 5-gallon Nano tank include bumblebee gobbies, coral or crown gobbies, dartfish or firefish gobbies, and shrimp gobbies. It’s important to note that gobbies should be kept in pairs only. If you put 3 together in a tank, 2 will often gang up and fight the remaining fish – usually to the death! Or the 2 dominate fish will bully the weaker one and force it into constant hiding, which will then likely cause its demise due to starvation.

What Can Live in a 5 Gallon Tank?

Cardinalfish are a great choice for a 5-gallon Nano tank. They’re often considered to be one of the best ‘starter’ saltwater fish for those who are new to the aquarium hobby. Reasonably priced and easy to care for, they have beautiful, bright color patterns that make them a welcome addition to any saltwater aquarium. Another neat feature is their tendency to carry their eggs in their mouths!

Apart from angelfish, gobies, and grammas, other aquatic creatures that can live in a 5-gallon saltwater tank include saltwater shrimp, blennies, anemones, and live rock,  As mentioned above, be careful with clownfish and chromis fish as they tend to bully other, smaller species. If you want to keep clowns or chromis’ in a 5-gallon tank, it’s best to keep just one – two at the most – since they breed rapidly.

What Size Tank Do You Need for a Saltwater Tank?

Many experienced aquarium hobbyists feel you should never keep saltwater fish in any tank smaller than 30 gallons, regardless of the size or species. The old adage of ‘bigger is better’ definitely applies to saltwater aquariums. The larger the tank, the more likely it is to sustain the daily fluctuations in water quality. In most cases, a 60-gallon tank is considered the best choice for a beginner saltwater aquarium.

Is it Hard to Maintain a Saltwater Tank?

Saltwater tanks are often more difficult to maintain than freshwater tanks. They’re also more expensive and require more time/effort. They need specific equipment to keep the marine ecosystem inside the tank balanced and healthy. Additional cleanings, special lighting and frequent water testing is necessary. If you’re new to the aquarium hobby, start with a small Nano tank until you get the hang of it.


To conclude, small marine fish that are non-territorial and have a calm demeanor can live in 5-gallon saltwater tank. The best choices are angelfish, cardinalfish, gobies, and grammas. Clownfish and chromis fish are other possibilities, however, these species tend to be more aggressive in nature. When it comes to saltwater aquariums, keep in mind that bigger is always better!

I hope this article has been helpful to you. Thanks for reading. Good luck with your aquarium.

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