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. Here are five of the most unusual fish you can keep in your 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 pearly, light-colored body has beautiful, dark marbling. Its pectoral fins are shaped like 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. 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 is a good match for other peaceful community fish, which swim in the bottom and middle layers of an aquarium. 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 includes freshwater gobies from Asia, Oceania. They are eel-like in shape and have about 2 inches (5cm) of length. 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 and frozen daphnia are their favourite foods. 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 peacock gudgeon gets its common name from its amazing array of rainbow colors. 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 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. They are generally mild-mannered, but males can be territorial during breeding season. It is easy to spawn them if both sexes are present and you provide 1-inch (22.5 cm) PVC pipes so they can lay their eggs.
4. Blind Cave Tetra
Astyanax mexicanus
In nature, this species actually comes in two forms – (1) a normal version found in rivers and lakes that looks like an ordinary, silvery tetra and (2) a blind cave version found in underground waterways and caverns in Mexico. The latter type is more popular in the aquarium hobby because of its shiny, pinkish body and undeveloped eyes covered by skin. They can still find food due to their improved senses of taste and smell. They also have the ability to navigate using their lateral lines, which detect changes in water pressure. This schooling fish is able to grow to about 3-3.5 inches (8-9cm), and can survive in a cool aquarium without heating. 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. Offer a variety of community foods like flakes, pellets, gel food, and frozen foods to keep them happy and well-fed.
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. Some species can survive in brackish water. This includes the top hat Blenny, which is a southern Japanese and Chinese species. 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. 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) long, elongated bodies is brown or grayish in color and ends with a yellow tail. Generally speaking, they are peaceful fish, but males will spar with their own kind over territory so provide rockwork and caves for them to seek shelter. They love brine shrimps, baby brine shrimps, dried seaweed, spirulina flakes, and algae that you scrape from the tank sides.
If you don’t have the space for a 10-gallon fish tank but love the idea of oddballs, we recommend our previous article. It covers our favorite nano-sized picks.