Rainbow Shark (Epalzeorhynchos frenatum)

Despite the name and the shark-like dorsal fin silhouette, rainbow sharks aren't sharks at all — they're a cyprinid, in the same broad family as goldfish and barbs, with the resemblance limited entirely to fin shape. Its territorial streak is specifically about claimed real estate: once it picks a cave or rock crevice as its own, it will aggressively defend that space against anything that looks similar, while generally leaving unrelated tankmates alone. A perennial favorite we stock for New Milford community tank owners. Multiples can live together, but only in a tank large enough that each one can hole up in its own cave without a clear sightline to the next — the fix for the aggression here is usually square footage, not luck.

Care level: Easy · Temperament: Semi-aggressive, territorial · Max size: ~6" · Min tank: 30 gal (add tank size for each additional fish kept together) · Diet: Omnivore, sinking pellets/veggies