20 Best Saltwater Fish for a 30 Gallon Tank

Finding the right fish for your tank can be an exhausting task, there are just too many beautiful fish out there! 30-gallon tanks are common. They’re the higher end of small tanks, and that makes them suitable for a wide range of diverse lifeforms. Today we’re going to focus on fish!

So buckle up and let’s dive in to take a look at the best saltwater fish for a 30-gallon tank.

saltwater fish tank

1. Ocellaris Clownfish

Max Size: 3”

# in 30 Gallon Tank: 2

Care Level: Easy

Diet: Omnivore

Special Requirements: None

The humble Clownfish is one of the best saltwater fish around. While their popularity skyrocketed after Finding Nemo hit the scene, they’ve got staying power thanks to their unique habits and excellent colors.

The Ocellaris Clownfish is one of the most common species of these fish. They reach about 3” in length, and you can safely keep a pair in a 30-gallon tank. They’re active, brilliant little fish that require a good bit of space but little in the way of specialized care. They’re even bred in captivity.

While not a shocking choice, Ocellaris Clownfishes are a common fish that are easy to care for. For beginners, it may be best to skip the anemone, however, as they’re far touchier than the fish that inhabit them. Instead, some corals may offer an easier solution.

2. Firefish Goby

Max Size: 3”

# in 30 Gallon Tank: 1

Care Level: Easy

Diet: Omnivore

Special Requirements: None

Firefish Gobies are magnificent little critters, defined by high-speed swimming, bright colors, and a surprisingly tall dorsal fin spike right at the front of the fin. Their distinctive looks have made them a fast favorite in the hobby and their care is relatively uncomplicated.

They range from 2-3” and are highly adaptable for saltwater species. They’re quite lively and get along with most fish. The only ones they don’t really get along with are other Firefish Goby, but they make great companions for clownfish and other peaceful marine denizens.

You’re going to need a tight hood for these guys since they’re known to jump, but apart from that? They’re excellent beginner fish with a unique look, and they’ll fit neatly into the environment of a 30-gallon tank. What’s not to love?

3. Royal Gramma

Max Size: 3”

# in 30 Gallon Tank: 1

Care Level: Easy

Diet: Planktivore

Special Requirements: None

Also known as the Fairy Basslet, these fish have a sharp divide in color which looks almost unnatural. Apart from their bright purple and yellow colors, they’re also very active and can add a lot of motion to the front of your tank. They reach about 3” in length, making them another solid choice for 30-gallon tanks.

These fish are usually quite peaceful, but they can be territorial over their hiding place. They’ll harass and chase off most other critters that decide to approach their specific spot but they rarely become problems outside of that specific instance.

One of the more interesting behaviors you might see is them swimming upside down underneath rocks and other decor objects. They seem to navigate the local terrain in their own unique way, inversion included. You’ll also need a strong hood if you keep a Royal Gramma due to their affinity for jumping.

4. Six Line Wrasse

Max Size: 3”

# in 30 Gallon Tank: 2

Care Level: Easy

Diet: Carnivore

Special Requirements: None

The Six Line Wrasse is a 4” reef fish with a lot of color and personality. These brilliant fish are easy to care for and do well in most marine tanks, including those with corals. As beginner fish they’re great, but you do need to be aware of some compatibility issues that they face.

The main problem is that the diminutive fish is actually a predator. While fine with corals, they may have problems with other invertebrates. The main culprit appears to be crabs, but problems with clams, shrimp, and anemones have also been reported so keep an eye out. In particular, they’ve been reported to go after hermit crabs. A bigger problem is housing them with other Wrasse and starting up territorial disputes.

The Six Line Wrasse hasn’t been successfully bred in aquariums as far as I can tell, though there are occasional reports of spawning in captivity. This can make them a little bit expensive but they’re hardy creatures with a long history of successful keeping in captivity, and it’s hard to beat their jewel-like looks.

5. Pajama Cardinalfish

Max Size: 3”

# in 30 Gallon Tank: 6+

Care Level: Easy

Diet: Omnivore

Special Requirements: See Below

Resembling the famous Bolivian Rams from freshwater aquaria, the Pajama Cardinalfish is a darting, shy schooling fish that does well in captivity. They swim in a different manner than most reef fish, staying still and then darting to the next location rather than slowly swimming like most others. They’re best kept in schools, and in a 30-gallon aquarium that will only leave you with stocking room for 1 or 2 other small fish.

The only real caveat to their care is that wild-caught specimens can be picky eaters. You may need to introduce the live foods they prefer along with what you plan to keep feeding them. Reduce the amount of live food over time and they’ll generally acclimate to eating the usual marine fish foods.

While they’ll take up most of the room in a 30-gallon tank, they’re a great pick for newbies. Fewer species also mean there are fewer potential problems, so it’s a great way to keep a fully stocked marine tank without balancing the needs of a dozen species of fish.

6. Lawnmower Blenny

Max Size: 4”

# in 30 Gallon Tank: 1 

Care Level: Intermediate

Diet: Deritrovore

Special Requirements: Well established tank

Moving away from the colorful reef denizens for a moment, we take a look at the Lawnmower Blenny. This is a specialized fish, often used as an algae eater in reef tanks, and it blends in well with the majority of substrates. They’re cool little fish, but some special care is required.

While they handily devour algae, the Lawnmower Blenny is actually a detritivore. In other words, they get the majority of their nutritional needs met through devouring rotted matter in the substrate. For that reason, a tank that contains one needs to be very well established. 30 gallons is on the small size for these fish due to their grazing needs, but it can be done if you’re careful.

While not the most active fish, you’ll find that Lawnmower Blennies are curious and will often study what’s going on outside the tank. They’ll mostly just hop from rock to rock and graze while they examine the world around them through large eyes. While not the most colorful reef denizen, Lawnmower Blennies are still among the most interesting.

7. Yellow Watchman Goby

Max Size: 4”

# in 30 Gallon Tank: 1

Care Level: Easy

Diet: Omnivore

Special Requirements: See Below

The Yellow Watchman Goby is one of the most impressive-looking shrimp gobies available. They’re bright yellow with blue spots, making a big visual impression, and they’re perfectly suited for a medium-sized tank. Their care is quite easy, and they’ll readily accept most commercial marine fish foods and frozen foods.

The main draw for many people is the symbiotic relationship displayed between shrimp goby species and pistol shrimp. In the wild, these fish partner up with pistol shrimp and act as a lookout for predators. In return, the pistol shrimp excavates a burrow that is used by both animals and the goby gets to eat parts of the shrimp’s prey.

While this relationship is always front and center, these fish can easily be kept without the shrimp. Like most gobies, they’ll be a beautiful bottom-dweller and a centerpiece in most tanks. It’s still worth the effort to track down a pistol shrimp to keep with them, as this amazing natural partnership can still happen in your own tank.

8. Banggai Cardinalfish

Max Size: 3”

# in 30 Gallon Tank: 1 Mating Pair

Care Level: Moderate

Diet: Carnivore

Special Requirements: None

The Banggai Cardinalfish is a small, fierce predator that hails from a small region of the world. They’re endangered in the wild, unfortunately, but they’re also one of the few saltwater fish that regularly breed in captivity.

Unfortunately, you can’t really keep a school in any reasonably sized tank. The males are fiercely territorial and will kill each other in the confines of an aquarium. A mated pair is fine to keep, but you’ll need to sex them. Sexing Banggai Cardinalfish isn’t easy, but they do display sexual dimorphism if you know what to look for.

Try to find captive-bred specimens if you’re looking to add these to your tank. Their wild capture has led to a crash in their numbers in the various locales they inhabit. That said, they’re beautiful, active fish as long as you’re aware of the problems with intraspecies aggression.

9. Purple Firefish

Max Size: 3 ½”

# in 30 Gallon Tank: 1

Care Level: Easy

Diet: Carnivore

Special Requirements: None

The Purple Firefish is another goby that comes in at a bit above 3” in length. They’re bright purple and red, creating an amazing color display when added to a tank. Like most gobies, they’re also territorial and can be a bit aggressive with others of their own species.

These fish are remarkably easy to keep. They’ll eat just about anything and get along well with most other reef denizens. Care should always be taken when introducing multiple species of goby to a tank, but with enough hiding spots, they should be able to coexist with other species in the family.

If you’re up for a real challenge, you can also try breeding these fish. It’s been done a few times, the main problem is making sure that you have the right sexes in the pair since they display no sexual dimorphism. Of course, just keeping them is its own reward, they’re a truly beautiful example of reef fish.

10. Coral Beauty Angelfish

Max Size: 4”

# in 30 Gallon Tank: 1

Care Level: Moderate

Diet: Omnivore

Special Requirements: Will nip at corals

The Coral Beauty Angelfish is a jaw-droppingly beautiful fish. Their deep coloration is unique, even among reef fish, and they have a graceful look to them. These beauties are, unfortunately, also prolific coral nippers so they may not be suitable for your reef tank.

With that out of the way, they can make a great display in the right tank. The main thing to be aware of is that they need plenty of room to swim, 30-gallons should be fine for one of these fish but you may need to move them to a bigger tank. The minimum tank size depends on who you ask, but there are definitely healthy specimens in 30-gallon tanks out there.

These fish are a bit more aggressive than many on this list, so their temperament needs to be accounted for. They should do fine with other semi-aggressive fish that will stand their own, but you should always have a backup plan in case it doesn’t work out. That said, their look is hard to beat despite the obstacles to keeping them.

11. Flame Angelfish

Max Size: 4”

# in 30 Gallon Tank: 1

Care Level: Moderate

Diet: Omnivore

Special Requirements: None

Much like the Coral Beauty Angelfish, the Flame Angelfish is an iconic and beautiful reef fish. Their coloration varies from red to orange, but all of them have semi-fluorescent blue tips to their fins and a lively personality. These are another semi-aggressive species, so care must be taken with choosing the right tankmates.

30-gallons is only suitable for a single one of these fish, and you don’t want to add them to a tank with another angelfish either. They’ll end up clashing and damaging each other in short order, and more passive fish will quickly be bullied by the Flame Angelfish. They’re not overly aggressive, just more so than most small marine fish.

If you can manage to keep their temperament in check, however, they’re great fish. They catch the eye from across the room and swim boldly in the open, so despite their presence limiting livestock in the tank you’ll still have one heck of an eyecatcher!

12. Royal Dottyback

Max Size: 2-3”

# in 30 Gallon Tank: 1

Care Level: Intermediate

Diet: Carnivorous

Special Requirements: Very individual levels of aggression

The Royal Dottyback is easily mistaken for the more easygoing Royal Gramma, since they share a similar bicolor pattern with closely matched colors. These fish are known for being individuals, and they’re also known for being a bit more fierce than their size would indicate.

Royal Dottybacks will square off with fish many times their size without blinking. That means keeping them requires individual assessments of any other fish added to the system. They need to be able to resist the Dottybacks attacks… and not eat the small Royal Dottyback.

They’re also predators when it comes to crustaceans, so care should be taken with choosing smaller shrimp and other invertebrates. If you can manage the aggression, however, these lively, courageous fish are always a hit in saltwater aquariums.

13. Striped Blenny

Max Size: 3 ½” to 4 ½”

# in 30 Gallon Tank: 1-2

Care Level: Intermediate

Diet: Omnivorous

Special Requirements: Need to be fed 2-3x daily

The Striped Blenny is among the various species of fang blenny. These fish have in common one thing: big, venomous fangs. The venom of the Striped Blenny is a very strange cocktail, primarily affecting opioid receptors. It’s a defensive weapon, these Blenny will only bite when cornered.

On the other hand, these are also peaceful and beautiful fish. The main attraction is how active they are, constantly swimming and hunting for food throughout the water column. This constant search also leads to very high-calorie use. These fish should be fed 2-3 times daily, rather than the usual once per day feeding to match their metabolism.

If you can manage that, however, then you’re in good hands. These fish are often captive-bred, and highly adaptable in the aquarium. Their active nature has made them a favorite for those keeping smaller tanks in the 20-50 gallon range.

14. Blue Spotted Jawfish

Max Size: 6”

# in 30 Gallon Tank: 1

Care Level: Intermediate

Diet: Carnivorous

Special Requirements: Coldwater marine fish, deep substrate

Despite the seeming tropical locality of their home, the Blue Spotted Jawfish is actually a coldwater fish. The waters in that region actually come down from Alaska, making them much colder than you’d expect from sunny Baja California. That means a chiller in most environments, to prevent these fish from succumbing to heat exhaustion.

Like all Jawfish, these colorful little guys dig in the substrate to form a den. That means you need several inches (generally 8”+) of debris and sand for them to dig into and form their burrow, this will keep the fish secure. You can make a pile of dead coral chunks, small pieces of rock, and sand instead of covering the entire bottom layer of the tank for the best results.

If you can manage their special requirements, they’re actually quite easy to care for. They’re colorful and their unique burrowing behavior is awesome to watch. That said, it’s best to make them the sole fish in the tank if you’re keeping 30 gallons to ensure they’re comfortable and secure.

15. Mollies

Max Size: 3 ½” 

# in 30 Gallon Tank: 6+

Care Level: Easy

Diet: Omnivores

Special Requirements: None

Yes, those mollies. It turns out that the humble live-bearing Molly is capable of living in marine environments. They’ll even thrive in it once they’re established. The only thing you need to do is make sure to use slow drip acclimation to get them used to the high salinity environment, the majority of them are kept in freshwater before being sold.

Mollies breed prolifically, and there are many varieties available. The larger Sailfin Mollies are particularly attractive, and they can be kept in medium-sized schools in a 30-gallon tank. They also make excellent dither fish, drawing out the less secure residents of your system.

While not the flashiest fish out there, Mollies are a solid choice in a marine aquarium. They excel as dither fish while having an unmistakable charm of their own. They’re one of the rare fish that seem to be able to survive in varying salinities, so keep them in mind when you’re putting together a saltwater community tank.

16. Green Mandarin Dragonet

Max Size: 3”

# in 30 Gallon Tank: 1

Care Level: Hard

Diet: Carnivorous

Special Requirements: Live foods

For many, these fish are the pinnacle of the hobby. They’re wild-caught, hard to keep, and many of them meet a bad fate due to inexperience. With sufficient research, however, you’re looking at one of the most beautiful fish around. The Green Mandarin Dragonet is only one of the various species of these gobies, there are others suitable for this size of tank as well.

These fish are very sensitive to water conditions. You need a well-established, stable tank that fits its required parameters. Make sure it’s been stable for some time before adding them. Problems with feeding are very common, make sure that you have a variety of live foods on hand to figure out what your fish will eat. They’re grazing predators, so it’s best that they have food available a few times per day.

On the other hand, these fish are also peaceful and reef-safe. If you’re up to the challenge of keeping them, the Dragonet will reward you with beautiful colors and their healthy life will stand to your accomplishments as an aquarist.

17. Starkii Damsel

Max Size: 3 ½”

# in 30 Gallon Tank: 1

Care Level: Easy

Diet: Omnivorous

Special Requirements: None

The Starkii Damsel is one of the many damselfish suitable for keeping in a 30-gallon aquarium. Damsels get a bit of a bad rap, often used as borderline throwaway fish to get tanks cycled but they’re awesome critters in their own right. The Starkii is a beautiful blue and yellow fish when healthy.

These fish are a bit aggressive. You can really only keep one damselfish of the same species in an aquarium, otherwise, they’ll fight constantly. They can also be a bit territorial, so the other fish in the tank need to be able to stand up to them. Fortunately, they’re not very big, so finding tankmates is easy enough.

Starkii Damsels are my favorite of the various damselfish and they’re an excellent choice for beginning saltwater aquarists. They’re hardy, colorful, and lively. All the hallmarks of a good fish to both capture a beginner’s interest and keep them advancing in the hobby!

18. Bicolor Blenny

Max Size: 4 ¼”

# in 30 Gallon Tank: 1

Care Level: Easy

Diet: Herbivore

Special Requirements: None

The Bicolor Blenny is a great choice for tanks in this size range. They’re peaceful fish with two tones, ranging from orange to a muddy blue, divided evenly down the middle. In addition, they’re a suitable fish for peaceful tanks and lack any real aggression.

These fish do tend to fight amongst themselves, so its best to keep only one per tank. On rare occasions, they may also nip other fish that look similar to them like firefish. This is an individual fish thing, so watch them carefully if you think there may be problems.

Other than that they’re another perfect beginner fish. Easy to feed, no special care requirements, and a lack of aggression are all great qualities. Adding one to a 30-gallon system is quite easy, especially if you’ve focused on adding non-aggressive specimens. 

19. Chalk Bass

Max Size: 4”

# in 30 Gallon Tank: 1

Care Level: Intermediate

Diet: Carnivore

Special Requirements: None

The Chalk Bass can be a handful, but they’re a beautiful fish that fits well in semi-aggressive tropical saltwater tanks. They will eat very small fish and invertebrates under 1” in size, so plan accordingly. These fish can hold their own with marine angelfish, who make good tankmates.

The Chalk Bass can be very aggressive with its own kind. It appears that 2 is the maximum number you can keep in a tank, and I recommend against doing so in a 30-gallon tank. A single Chalk Bass will do well enough, they don’t need a school to protect them. Some people have kept them in larger tanks by dropping in a group of 5 or more, but this doesn’t seem to be viable long term.

For semi-aggressive tanks in this size range, they’re just about perfect. They don’t closely resemble any other species, they can tangle with other fish their size, and they’re very easy to keep alive and even breed in captivity.

20. Ruby Red Dragonet

Max Size: 2 ½”

# in 30 Gallon Tank: 1

Care Level: Advanced

Diet: Carnivorous

Special Requirements: Specialized feeding

The Ruby Red Dragonet is the smallest of the mandarin fish species, coming in at 2 ½” at maximum. They’re beautiful, intricately colored fish that are also among the hardest to keep in aquaria. The Green Dragonet is actually just a bit easier to keep, although both require a very experienced aquarist.

In a weird twist: these fish were already being kept before being described scientifically. Their feeding is extremely complicated, requiring a constant supply in the tank. The tank should be fully cycled and have been running for at least 6-9 months before the Ruby Red Dragonet is introduced.

They’re among the hardest marine fish to keep in captivity, but it can be done. Just be aware that the research and time needed are a serious investment, even more so than the other related species of dragonet. If you can keep one alive for its natural lifespan, however, you can truly call yourself a saltwater aquarium expert.

Stock Your 30-Gallon With the Best Fish

The best saltwater fish for 30-gallon tanks are all over the place. From the tiny dragonets to the fierce Dottyback and even the humble Molly… all will do well in a mid-sized marine enclosure. It’s just a matter of making sure that you know what you’re getting into.

So, which of these fish are going to make their home in your tank?