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 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 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 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.

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. You can make them more comfortable by adding floating plants such as water sprite to their shelter. Also, try getting a school of six or more marbled hatchetfish. This species pairs well with other peaceful community fish that swim in the middle and bottom layers of the aquarium. Because of their small mouths, feed tiny floating foods like crushed flakes, Easy Fry and Small Fish Food, baby brine shrimp, 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. Their favorite foods include Repashy Soilent Green, frozen daphnia, baby brine shrimp, algae wafers, and canned green beans. 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

Because of its incredible rainbow colors, the peacock gudgeon is commonly known as the “peacock gudgeon”. Imagine a pink, 2.5-inch (6cm) body with yellow speckling, red vertical stripes and yellow-rimmed fins. There is also a black spot at its base. 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 originate from Papua New Guinea. They prefer the lower half of an aquarium. However, they don’t have a preference for particular foods and will happily eat all floating and sinking community food items you provide. While they are normally mild-mannered fish, males can become territorial during breeding seasons. If you have both males, they can be sexed and provided with 1-inch (2.5 cm), PVC pipes to help them lay their eggs.

4. Blind Cave Tetra

Astyanax mexicanus

The species is actually found in two versions in nature. There’s a (1) normal version that can be found in rivers or lakes, which looks like an ordinary, silvery Tetra, and (2) blind cave versions found underground and in caverns in Mexico. Because of its shiny, pinkish appearance and skin-covered eyes, the latter is more popular in aquariums. Despite the blindness, they can easily find food with their enhanced senses of smell and taste and navigate by using their lateral lines to detect changes in water pressure. 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. Although they are considered a good community fish, they can be aggressive and will nip at anything to explore their surroundings. Keep them away from slower-moving fish or those with long fins. 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 mainly found in saltwater habitats. This is a shame for freshwater hobbyists as they have so many interesting personalities and behaviors. There are some species that can live in brackish waters, such as the top-hat blenny from China and southern Japan. 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) elongated body is a brown or grayish color that ends in a yellow tail. They are usually peaceful fish. But males may fight over territory so they need rockwork and caves to shelter them. Their favorite foods include brine shrimp, baby brine shrimp, dried seaweed, spirulina flakes, and even algae you scrape off 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.