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? 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 come from tannin-filled black waters in the Amazon basin of South America, which tends to have acidic pH and tropical temperatures, but they are accustomed to handling a wide range of water parameters because the area is subject to annual flooding.

The hatchetfish is a top-dwelling fish, capable of leaping out of water to escape predators. Keep your aquarium closed tightly and cover any gaps with craft mesh. 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. 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. For more details, see our hatchetfish care guide.

2. Stiphodon Goby

Stiphodon ornatus

The Stiphodon genus consists of freshwater gobies from Asia and Oceania that have a slender, eel-like body similar to kuhli loaches but with half the length at around 2 inches (5 cm) long. 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. While Stiphodon gobies are excellent community fish, the males can sometimes be a bit feisty towards one other, so provide plenty of hiding spots and consider getting more girls than boys, even though the females are less colorful.

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. The males have an obvious nuchal hump on the forehands, as seen in the photo above. While the females have more of a streamlined forehead, much like a typical tetra and danio, 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. 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

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. 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 resilient schooling fish grows to around 3-3.5 inches (8-9 cm) and can live in a cool water aquarium with no 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. Some species can survive in brackish water. This includes the top hat Blenny, which is a southern Japanese and Chinese species. While they are often called a freshwater blenny by some, their preference is for brackish water that has a higher pH and GH. As per their common name, males have a rounded crest atop their head, and their entire head and face has a striking pattern of vertical, yellow striping. 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. 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.