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This group collects the freshwater fish that do not fit a classic family but are popular in the hobby: from tiny scarlet badis to bichirs that look like living fossils. Many of them have special needs, so read each profile carefully before buying.
- Marbled hatchetfish: surface schooling fish that need a tight lid and calm tank mates.
- Pea puffer: tiny but predatory and nippy; best in a species tank, fed snails and frozen foods.
- Black ghost knifefish: nocturnal, grows to around 18 inches (45 cm) and needs a very large tank.
- Glass catfish: transparent, shy schooling fish that need a group and gentle flow.
- Butterfly fish and bichir: predators that eat any fish small enough to swallow.
- Scarlet badis and badis badis: small micro predators that often prefer live or frozen food.
- Synodontis petricola and spiny eel: nocturnal bottom dwellers with specific setups.
The common thread is that most of these species are not plug-and-play community fish. Check the adult size, diet and temperament on each profile, use the compatibility checker, and choose tank mates that will neither bully them nor end up as food.
Other aquarium fish
| Species | Min. liters | Size | Temp. | Difficulty |
|---|---|---|---|---|
 African butterflyfish Pantodon buchholzi | 32 gal (120 L) | 3.9 in (10 cm) | 75–84 °F (24–29 °C) | Moderate |
 Badis Badis badis | 16 gal (60 L) | 2.4 in (6 cm) | 68–79 °F (20–26 °C) | Moderate |
 Black ghost knifefish Apteronotus albifrons | 132 gal (500 L) | 17.7 in (45 cm) | 73–82 °F (23–28 °C) | Difficult |
 Glass catfish Kryptopterus vitreolus | 32 gal (120 L) | 2.6 in (6.5 cm) | 72–79 °F (22–26 °C) | Moderate |
 Marbled hatchetfish Carnegiella strigata | 21 gal (80 L) | 1.4 in (3.5 cm) | 75–82 °F (24–28 °C) | Moderate |
 Pea puffer (dwarf puffer) Carinotetraodon travancoricus | 8 gal (30 L) | 1.2 in (3 cm) | 75–82 °F (24–28 °C) | Moderate |
 Peacock eel Macrognathus siamensis | 53 gal (200 L) | 9.8 in (25 cm) | 73–82 °F (23–28 °C) | Moderate |
 Scarlet badis Dario dario | 11 gal (40 L) | 0.8 in (2 cm) | 64–79 °F (18–26 °C) | Moderate |
 Senegal bichir Polypterus senegalus | 79 gal (300 L) | 11.8 in (30 cm) | 75–82 °F (24–28 °C) | Moderate |
 Synodontis petricola Synodontis petricola | 53 gal (200 L) | 4.3 in (11 cm) | 73–81 °F (23–27 °C) | Moderate |
No species match those filters.