Top 5 Oddball Fish for A 20-Gallon Aquarium

Top 5 Oddball Fish for a 20-Gallon Aquarium Looking for a fish that is bizarre in appearance, has unique behaviors, or is rarer in availability? In the aquarium hobby, we have a whole category dedicated …


Top 5 Oddball Fish for a 20-Gallon Aquarium

Looking for a fish that is bizarre in appearance, has unique behaviors, or is rarer in availability? In the aquarium hobby, we have a whole category dedicated to these “oddball fish.” Some species are quite hardy and easy to keep, while others have specialized care requirements to accommodate their unusual physiology. Find out about five of the most bizarre fish that you can keep within a 20-gallon tank.

1. Marbled Hachetfish

Carnegiella strigata

This species measures in at 1.25 inches (3cm) and features a prominent chest that resembles a hatchet blade. Its pearly, light-colored body is covered in beautiful, dark marbling, and the pectoral fins stretch out like little wings. They are native to the Amazon basin in South America. The area is subject to flooding each year, and the water they come from is black, tannin-rich waters.

Because hatchetfish are top-dwelling fish that are capable of jumping out of the water to escape predators, make sure to have a tight-fitting lid on the aquarium and cover any little openings with craft mesh or other materials. If you want them to feel more comfortable, put floating plants like water-sprite in their aquarium. You should also get at least six marled hatchetfish in your school. This species can be paired with peaceful community fish that live in the aquarium’s middle and bottom layers. You can feed them tiny floating foods such as crushed flakes, easy fry and small fish food, baby brine shrimp and daphnia because of their small mouths. For more details, see our hatchetfish care guide.

2. Stiphodon Goby

Stiphodon ornatus

Stiphodon genus is a group of freshwater gobies that hail from Asia and Oceania. They have a slim, eel-like body, similar to kuhli loaches, but about half their length at 2 inches (5 cm). Like otocinclus catfish, they are aufwuchs grazers, meaning they like to constantly forage on algae, zooplankton, and biofilm found growing on surfaces. Repashy Soilent Green is their favorite food. They also love frozen daphnia and baby brine shrimp. Stiphodon gobies make great community fish. However, males can be a little feisty towards each other so give them plenty of hiding places and think about getting more girls than the boys.


3. Peacock Gudgeon

Tateurndina ocellicauda

The peacock gudgeon gets its common name from its amazing array of rainbow colors. Imagine a 2.5-inch (6 cm), pink body with red vertical stripes, blue speckling, yellow-rimmed fins, and a black spot at the base of the tail. As you can see in the above picture, males have a distinctive nuchal hump in their forehands. Females have a more straight forehead similar to a tetra or danoio. They come from Papua New Guinea and tend to dwell in the lower half of the aquarium. However, they don’t have a preference for particular foods and will happily eat all floating and sinking community food items you provide. They are generally mild-mannered, but males can be territorial during breeding season. They are quite easy to spawn if you have both sexes and provide 1-inch (2.5 cm) PVC pipes for them to lay their eggs.

4. Blind Cave Tetra

Astyanax mexicanus

This species can be found in two types in nature. One is a regular version that lives in rivers and lakes and looks similar to a silvery tetra, and the other is a blind cave version that lives underground in Mexico’s caverns and waterways. This latter variety is more common in aquarium hobby due to its shiny, pinkish body with undeveloped eyes that are covered by skin. Despite being blind, they are able to find food easily with their enhanced senses. The schooling fish can grow to approximately 3-3.5 inches (8-9cm) in length and can be kept in cool water without a heater. They are considered to be a common fish. However, they will often nip at objects to inspect their surroundings. Keep them happy with a variety community food like pellets, gel foods, and flakes.

5. Top Hat Blenny

Omobranchus fasciolatoceps

Blennies predominently come from saltwater habitats, which is a shame for freshwater hobbyists because they have such fun personalities and interesting behaviors. Luckily, there are some species that live in brackish water, like the top hat blenny that comes from southern Japan and China. They are often marketed as a freshwater blenny, but in our experience, they do best in brackish water with alkaline pH, higher GH, and tropical temperatures. According to their common name, males have an oval crest at the top of their heads, and their entire face and head are decorated with vertical, yellow stripes. The rest of their 2.5 to 3 inch (6-8 cm) long, elongated bodies is brown or grayish in color and ends with a yellow tail. They are usually peaceful fish. But males may fight over territory so they need rockwork and caves to shelter them. They love brine shrimps, baby brine shrimps, dried seaweed, spirulina flakes, and algae that you scrape from the tank sides.

If you are looking for oddball fish and don’t have enough space to put up a 10-gallon tank, our previous article will help you find some of our top picks.