Buying a Used Reef Tank: What to Check Before You Hand Over Cash

A used setup can save you half the cost of new. It can also hand you someone else's leak, pest outbreak, and failing equipment.

Inspect the tank itself

• Silicone seams: look for peeling, gaps, or bubbles along the inside edges. Scratched glass is cosmetic, but bad seams are not.
• Ask to see it full and running. A tank that's already drained can't show you a leak.
• Check the stand for water damage, swelling, or rot, especially at the base.

Inspect what's living in it

• Pests hitchhike on rock: aiptasia (small brown anemones), flatworms, bristleworm overload, nuisance algae. Some are manageable, and some take months to clear.
• Ask how long the tank has been running and why they're selling. "Moving" is fine, while "it keeps crashing" tells you a lot.

Inspect the equipment

• Ask the age of pumps, heaters, and lights. Heaters are cheap to replace and expensive when they fail.
• Confirm the sump volume and plumbing actually fit your space.

The move is its own job. Moving livestock, rock, and sand without crashing the tank takes planning, including containers, keeping bacteria alive, and re-establishing flow fast. This is the part most people underestimate.