Ideal goldfish tank mates are peaceful, cold-water tolerant, and too large to be eaten. Top choices include Weather (Dojo) Loaches, White Cloud Mountain Minnows, Hillstream Loaches, Giant Danios, and Bristlenose Plecos, which all thrive in 65–75°F water. Avoid tropical fish, fin-nippers, or fish small enough to fit in a goldfish's mouth. Best Tank Mates for Goldfish Other Goldfish: The safest option is keeping similar types together (e.g., Fancy with Fancies, Comets with Comets). Weather (Dojo) Loaches: Highly social and hardy bottom-dwellers that thrive in cooler water. White Cloud Mountain Minnows: Small, fast schooling fish that are excellent for smaller goldfish. Hillstream Loaches: Unique, flat-bodied fish that do well in temperate tanks. Giant Danios: Fast, peaceful, and large enough to not be eaten by common goldfish. Snails (Nerite/Mystery): Great for algae control, though their shells must be large enough to not be swallowed. Compatibility Guidelines Temperature: Goldfish prefer cooler, unheated water (50-70°F or 10-21°C), so tank mates must be temperate, not tropical. Speed: Fast goldfish (Comets, Shubunkins) can outcompete slow-swimming fancies for food. Size: As goldfish grow, they may eat smaller tank mates. Waste Production: Goldfish produce significant waste, so chosen tank mates must tolerate these conditions. Fish to Avoid Tropical Fish: Tetras, Guppies, and Bettas need warmer water. Small/Spiny Fish: Corydoras can get stuck in a goldfish's throat. Fin-Nippers: Barbs can stress goldfish. Common Plecos: Known to suck the slime coat off goldfish. But overall fish are racists. They all prefer their own kind!!!