BEGINNER-FRIENDLY ODDBALL FISH: UNIQUE SPECIES THAT WORK IN SMALL TANKS

What Are “Oddball” Fish—and Are They Beginner-Friendly?

“Oddball” is a loose term aquarists use for fish that don’t fit into the usual community categories. They might have unusual body shapes, rare behaviors, or come from niche habitats. Classic examples include pea puffers, killifish, and tiny labyrinth fish like sparkling gouramis.

While some oddball fish require advanced care, there are several species that are surprisingly hardy and well-suited to beginners—as long as their basic needs are met:

• Soft to moderately hard, stable water
• Proper tank size and layout (hiding spots, plants, low flow)
• Species-appropriate diet (some prefer live or frozen food)
• Thoughtful tankmates, or single-species tanks in smaller setups

If you’re new to fishkeeping, it’s still worth reviewing the basics in our beginner aquarium tips guide before jumping into oddball species.

Setting Up a Small Tank for Oddball Fish

Oddball fish often feel more secure in heavily planted, softly lit tanks. Many of them come from shaded streams, forest puddles, or slow-moving backwaters. You don’t need anything fancy, but a few key setup details make a big difference.

• Tank Size: Most of the species below can thrive in 5–15 gallon aquariums. When in doubt, go larger.
• Filtration: Use a gentle sponge filter or adjustable hang-on-back filter—avoid strong current.
• Lighting: Moderate lighting with floating plants or tall stems for shade (read our aquarium lighting guide).
• Hardscape & Plants: Driftwood, caves, and live plants like Java fern, Anubias, and Cryptocoryne provide cover.
• Water Parameters: Aim for stable temperature (74–80°F for most oddballs) and good water quality with 0 ammonia and nitrite. See our water parameter guide for details.

Most oddball fish are sensitive to sudden changes, so always acclimate them slowly using drip or cup acclimation methods. You can follow the same steps in our acclimation guide.

Oddball Species That Work in Small Tanks

Let’s look at specific fish that bring “wow” factor to nano aquariums while still being relatively beginner-friendly.

Sparkling Gourami (Trichopsis pumila)

• Adult Size: ~1.5 inches
• Minimum Tank: 5 gallons (better in 10+ for groups)
• Temperament: Peaceful but shy; best in calm, planted setups

Sparkling gouramis are tiny labyrinth fish with iridescent blue spangling and copper tones. They’re famous for their subtle “croaking” sounds during courtship and territorial displays. These fish prefer dim lighting, lots of plants, and gentle flow. A trio (1 male, 2 females) in a 10-gallon planted tank makes a stunning oddball centerpiece.

Clown Killifish (Epiplatys annulatus)

• Adult Size: ~1–1.5 inches
• Minimum Tank: 5 gallons (longer tanks preferred)
• Temperament: Peaceful top-dwellers

Clown killifish are tiny, rocket-shaped surface swimmers with striking tail patterns that resemble flags. They do best in tanks with a tight lid (excellent jumpers) and plenty of floating plants. A small group of 6 in a 10-gallon tank works well. Feed them small foods like crushed flakes, baby brine shrimp, and micro-pellets.

Scarlet Badis (Dario dario)

• Adult Size: ~0.8–1 inch
• Minimum Tank: 5 gallons for a single male; 10+ gallons for a small group
• Temperament: Shy, semi-territorial males

Scarlet badis are tiny, jewel-like fish with vivid red and blue striping. Males display to each other and enjoy picking through plants and leaf litter. They’re picky eaters and strongly prefer live or frozen foods (daphnia, cyclops, baby brine shrimp). They’re best for slightly more patient beginners willing to offer quality foods regularly.

Pea Puffer (Carinotetraodon travancoricus)

• Adult Size: ~1 inch
• Minimum Tank: 5 gallons for one; 10 gallons for a small group
• Temperament: Curious, territorial, nippy

Pea puffers are classic oddball nano fish: big eyes, round bodies, and huge personalities. They’re intelligent and interactive but can be fin-nippers, so they usually do best in species-only tanks. They require frequent feeding of meaty foods like snails, frozen bloodworms, and brine shrimp. Heavily plant and hardscape the tank to break up lines of sight and reduce aggression.

Bumblebee Goby (Brachygobius spp.)

• Adult Size: ~1–1.5 inches
• Minimum Tank: 10 gallons
• Temperament: Mildly territorial, bottom-dwelling

These black and yellow banded gobies are eye-catching but a bit more specialized. Many species prefer brackish or slightly brackish conditions, though some are kept in freshwater. They love sandy substrates, caves, and live or frozen foods. They’re best in species-only or carefully planned setups once you’re comfortable with basic water chemistry.

African Dwarf Frog (Hymenochirus spp.) – Oddball Bonus

• Adult Size: ~2 inches
• Minimum Tank: 10 gallons for a small group
• Temperament: Peaceful, fully aquatic amphibian

While not technically a fish, African dwarf frogs are a popular oddball choice for small tanks. They live fully underwater but must surface for air. They’re best kept in frog-only or very calm community setups, since they’re poor competitors for food. Feed them sinking pellets, frozen bloodworms, and careful target feeding with tongs or a turkey baster.

Stocking Plans for Small Oddball Tanks

Because many oddballs are shy, territorial, or have special diets, smart stocking is crucial. Here are sample stocking plans that work well in real-world tanks:

5-Gallon Oddball Ideas

• 1 Pea Puffer (species-only, heavily planted)
• 1 Male Betta + 3–4 small snails (if temperament allows, not for puffers)
• 1 African Dwarf Frog pair (with careful feeding and secure lid)

10-Gallon Oddball Ideas

• Trio of Sparkling Gouramis + shrimp or snails
• 6 Clown Killifish + small shrimp colony (if shrimp are well-established)
• 3 Pea Puffers (1 male, 2 females) in a heavily planted, species-only tank
• 1 male Scarlet Badis + 2–3 females, with dense plants and leaf litter

15–20 Gallon Oddball Community

• 6 Clown Killifish (surface)
• 3–4 Sparkling Gouramis (mid/upper)
• 1 group of shrimp or a few Nerite Snails (cleanup crew)

Always research each species’ needs before mixing them. For broader guidance, refer to our freshwater community compatibility guide.

Compatibility and Care Considerations

Oddball fish are often labeled “semi-aggressive” or “specialized,” but many issues come from poor stocking or setup. Keep these rules in mind:

• Avoid fin-nipper + long-fin combos: Puffers, some badis, and nippy species shouldn’t be housed with bettas or fancy guppies.
• Respect feeding styles: Slow feeders (African dwarf frogs, scarlet badis) struggle with fast fish.
• Provide hiding places: Caves, dense plants, and wood reduce stress and aggression.
• Match water parameters: Don’t mix soft-water oddballs with very hard-water species.
• Skip high-traffic tanks: Oddballs often dislike constant movement and bright light.

Oddball success is less about perfect water chemistry and more about thoughtful environment design and consistent care.

Feeding, Maintenance, and Common Mistakes

Many oddballs lean toward carnivorous diets, so feeding is more involved than simply tossing in flakes.

• Offer frozen or live foods several times per week (bloodworms, brine shrimp, daphnia).
• Use feeding tongs or a turkey baster for targeted feeding of shy species.
• Perform weekly 20–30% water changes to manage waste from high-protein diets.
• Test water regularly during the first month after adding oddballs to your tank.

Common mistakes include:

• Adding oddballs to busy community tanks where they are bullied or outcompeted.
• Skipping research on whether a species prefers brackish vs freshwater.
• Overstocking small tanks that don’t dilute waste quickly.
• Ignoring lids—many oddballs are jumpers or climbers.

Takeaway: Unique Fish, Manageable Care

Oddball fish bring personality, uniqueness, and a sense of discovery to small aquariums. With the right species, thoughtful stocking, and a planted, low-stress environment, they can be just as beginner-friendly as more common community fish. Start with one of the species above, design your tank around its needs, and enjoy watching your tiny, unusual residents explore their underwater world.

To turn your oddball tank into a true showpiece, pair this guide with our aquascaping for beginners article and create a layout that makes your unique fish the stars of the show.