Top 5 Oddball Fish for A 20-Gallon Aquarium

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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? These fish are a special category in the aquarium hobby. Some species are hardy and simple to keep, others require special care to adapt to their unique physiology. Learn about 5 of the coolest oddballs that you can keep in a 20-gallon aquarium.

1. Marbled Hachetfish

Carnegiella strigata

This hatchetfish is a tiny species measuring 1.25 inches (3 cm). It has a prominent chest, resembling a hatchet knife. The body of this pearly-white hatchetfish is covered with beautiful, dark marbling. The pectoral fins extend out like tiny wings. They were born in tannin-rich black waters of the Amazon basin, South America. These waters tend to be acidic and tropical, but they are used to handling all water parameters.

Hatchetfish are top-dwelling fish and can jump out of the water to escape predators. Make sure your aquarium has a tight-fitting lid. Cover any openings with craft mesh, or other materials. To help them feel more comfortable, add floating plants like water sprite as shelter and get a school of at least six marbled hatchetfish because the more the merrier. This species is a good match for other peaceful community fish, which swim in the bottom and middle layers of an aquarium. Small mouths make it difficult to feed these fish small floating foods like Easy Fry and Small Fish Feed, crushed flakes and baby brine shrimps and daphnia. See our hatchetfish care manual for more information.

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). They are also aufwuchs grazers like otocinclus catsfish. This means that they eat algae, zooplankton and biofilm on surfaces all the time. Repashy Soilent Green is their favorite food. They also love frozen daphnia and baby brine shrimp. Stiphodon gobies can be great community fish. The males can sometimes be a bit aggressive towards each other. Provide plenty of hiding spots for them and consider getting more females than boys.

3. Peacock Gudgeon

Tateurndina ocellicauda

The amazing rainbow colors of the peacock-gudgeon are what gave it its name. Imagine a pink 2.5-inch (6 cm) body with blue vertical stripes, blue spekling and yellow-rimmed 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 are native to Papua New Guinea, and they prefer to live in the lower part of the aquarium. That being said, they are not picky eaters and are happy to consume any floating and sinking community fish foods you feed them. 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. Because of its shiny, pinkish appearance and skin-covered eyes, the latter is more popular in aquariums. 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. While they are rated as a community fish, be aware that they like to nip at things to investigate their surroundings, so keep them away from slow-moving or long-finned fish. To keep them happy and healthy, provide a variety of community food options, including flakes, pellets and gel food.

5. Top Hat Blenny

Omobranchus fasciolatoceps

Blennies are most commonly found in saltwater habitats. This is unfortunate for freshwater hobbyists since they have such interesting personalities. There are some species that can live in brackish waters, such as the top-hat blenny from China and southern Japan. Although they are sometimes marketed as a freshwater species, we have found that they thrive in brackish water with higher pH, higher GH and tropical temperatures. Their common name refers to a male with a round crest on their head. The entire head and face of the males are covered in a striking pattern vertically striped yellow. The rest of their 2.5- to 3-inch (6-8 cm) elongated body is a brown or grayish color that ends in a yellow tail. They are generally peaceful fish. However, males can be territorial so make sure to provide rocks and caves for them shelter. 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.