Fancy Goldfish Bullying in a Small Tank: Space Matters

Why Is My Telescope Goldfish Bullying the Smaller One?

A 10-liter tank (about 2.6 gallons) is far too small for even one fancy goldfish, let alone two. The "bullying" you're seeing—nudging, hiding, lying on the side—is almost certainly stress from extreme overcrowding and poor water quality.

Goldfish Space Requirements

• Minimum: 10–20 gallons (38–76 liters) per fancy goldfish.
• Ideal: 30+ gallons for a pair, with strong filtration.
• Growth: Fancy goldfish can reach 6–8 inches and produce heavy waste.

Why the Bowl Is Worse

A bowl has no filtration, minimal surface area for gas exchange, and rapid temperature swings. It's a death sentence for goldfish.

Immediate Steps

1. Upgrade to at least a 100-liter (26-gallon) tank with a quality filter.
2. Add hiding places (plants, caves) to reduce territorial behavior.
3. Test water daily for ammonia and nitrite during the transition.
4. Feed a varied diet including sinking pellets and vegetables (peas, zucchini).

With proper space and conditions, goldfish are peaceful. The aggression you're seeing is a cry for help—not malice.

Learn more at Goldfish Care Guide.