Many different species of fish are available to keep in a saltwater aquarium. Searching the internet to find the perfect fish can be an incredible challenge. The amount of information out there can make your head spin. This guide will help you get closer to finding the right fish for your saltwater fish tank. Although many of these fish will not be compatible with one another in such a small fish tank, you’ll at least get an idea of the many fish to choose from.
1. Firefish
Firefish are relatively common and a more popular fish found in saltwater aquariums. They are peaceful fish that hang out above live rock and will dart into the rockwork when startled. They are generally timid fish and choose to hide when stressed. They are known to be jumpers, so keeping a well-fitted lid on your fish tank is highly recommended.
There are a few different species of Firefish, the most common ones are the Firefish (Nemateleotris magnifica) and Purple Firefish (Nemateleotris decora). Less common species of Firefish are the Helfrichi Firefish (Nemateleotris helfrichi) and the Exquisite Firefish (Nemateleotris exquisita). Generally, each species will have similar water parameter requirements and grow to similar sizes.
2. Clown Goby
The Clown Goby is an interesting fish and is often found resting on corals and rockwork for minutes to hours at a time. They are generally very docile and should not bother other fish in the aquarium. However, they may battle it out amongst themselves in smaller fish tanks. They are generally reef-safe but will nip and bother many stony corals such as Acropora, and possibly others.
There are a few different types of Clown Gobies available. The Citrinis Clown Goby (Gobiodon citrinus), is also known as the Citrin Goby or the Yellow Clown Goby. This species, as the name suggests has a yellow coloration to it. Next, is the Green Clown Goby (Gobiodon atrangulatus), which has a mosaic of green, orange, and yellow colors on its body. There is also the Black Clown Goby (Gobiodon strangulatus). This species has a black/blue color to it. Last, is the Panda Goby (Paragobius lacunicolus), which has a yellow and orange body with black fins. You can click on any of their names to check out their complete care guides.
3. Neon Goby
Neon Gobies (Elactinus oceanops) are incredibly small saltwater fish that would do great in a 20-gallon aquarium. They have black, white, and vibrant blue horizontal stripes on their body. They will generally not bother other species of fish in an aquarium, but they become territorial and will likely pick fights with their own species.
In the wild, they pick parasites off other fish, but that’s not always possible in an aquarium. Because of this, the Blue Neon Goby should be fed a variety of Mysis Shrimp, Brine Shrimp, and other frozen foods made for carnivores. They should also be fed at least once a day, but twice a day is optimal.
4. Mexican Barnacle Blenny
Mexican Barnacle Blennies (Acanthemblemaria macrospilus) are communal saltwater fish and a great choice for a 20-gallon saltwater aquarium. Although they are not as active as most other fish, they’re still a fantastic option. Mexican Barnacle Blennies spend most of their time poking their heads out of crevices in rocks, waiting for food to be put into the aquarium. They will then quickly dart out of the rock and grab the food. The fun part about keeping this fish species is trying to find where they are hiding.
5. Possum Wrasse
The Possum Wrasse, sometimes called the Pygmy Wrasse, is an excellent choice for a 20-gallon aquarium because of their unique shape, coloration, and peaceful nature. On top of that, they will hunt for nuisance worms and other microorganisms that may be problematic in your aquarium. They should not bother coral in the aquarium.
There are two types of Possum Wrasse available. The Yellow Banded Possum Wrasse (Wetmorella nigropinnata) and White Banded Possum Wrasse (Wetmorella albofasciata). Both have similar temperaments and dietary needs. However, the coloration and patterns of both species are different. Check out the Yellow Banded Possum Wrasse – Complete Care Guide for more information on this fish.
6. Yasha White Shrimp Goby
The Yasha Goby (Stonogobiops yasha) is an excellent sand-sifting fish for a 20-gallon saltwater aquarium. They have beautiful white, orange, and red colors throughout their bodies and they only grow to about 2.5″. As a bonus, similar to a Watchman Goby, you can pair a Yasha Goby and Pistol Shrimp together to create a symbiotic relationship. There’s nothing better than watching a goby standing guard, while the pistol shrimp is working hard excavating.
Unfortunately, this goby isn’t as common in the hobby as many other species of goby. With patience, you’re likely to find one for sale from time to time.
7. Yellow Watchman Goby
Yellow Watchman Gobies (Cryptocentrus cinctus) are fantastic sand sifters for 20-gallon aquariums. They create burrows along rockwork and spend most of their time excavating and protecting them. The Yellow Watchman Goby is a great fish to pair with a pistol shrimp, but beware because this fish is known to jump out of aquariums. You’re welcome to learn more about this fish by taking a look at the Yellow Watchman Goby – Complete Care Guide.
8. Pink Streaked Wrasse
The Pink Streaked Wrasse (Pseudocheilinops ataenia) is another gorgeous fish that is a great choice for a saltwater aquarium. It is reef-safe and only grows to 2.5″. This species of wrasse has blue, red, and yellow colorations with horizontal streaks spread across its body. Unlike similarly looking Sixline Wrasses, this species should not be aggressive towards other fish. You can learn more about this fish by checking out the Pink Streak Wrasse – Complete Care Guide.
9. Deepwater Candy Basslet
If you have deep pockets and a cool water aquarium, check out the Deepwater Candy Basslet (Liopropoma carmabi). This gorgeous fish has predominately yellow and pink/lavender horizontal streaks. It will grow to about 2.5″ in length and will do best with varying pieces of live rock to use for cover. It is generally peaceful and is mostly reef-safe, but crustaceans that fit into its mouth may become a meal for this fish.
10. Swissguard Basslet
The Swissguard Basslet (Liopropoma rubre) is a gorgeous red, black, and orange saltwater fish with horizontal stripes throughout its body. It grows to about 3″ at full size when it is fully grown. It does best with live rock with plenty of caves and crevices to hide in because this species is known to be fairly shy. It is generally reef safe but may pick on smaller crustaceans.
11. Royal Gramma Basslet
The Royal Gramma Basslet (Gramma loreto) is a vibrant purple and yellow saltwater fish that will do great in a 20 gallon reef tank. It is considered a great beginner fish due to its hardy nature. This species of fish does best in aquariums with an assortment of live rock that it can use for cover. It will protect its territory from other fish.
Final Notes
Hopefully, this list gives you a good idea of the assortment of fish that can be kept in a 20-gallon saltwater aquarium. As a disclaimer, you cannot cram all these fish into a single 20-gallon fish tank. Many of them will not do well together in such a small fish tank, because of potential territorial disputes. This list is made to showcase what’s out there, and more research is needed to figure out what will do well together. If you already have your saltwater fish tank stocked with fish, check out some fantastic Clean Up Crew Options for Saltwater Aquariums!