Emergency playbook

Reef tank leaking or flooding: what to do now

Water and mains electricity together are the real danger here. People first, then the tank.

Why each step

1. If water has reached sockets or extension leads, do not touch them. Switch off at the consumer unit (fuse box).

Our reading: salt water conducts well, and a wet socket can make the floor live.

2. Otherwise switch off and unplug everything near the water at the wall, starting with the return pump.

Stopping the return shows whether the leak is in the sump or the display.

3. Find the leak: watch which level falls with the return off.

A sump overflowing after the return stops is a back-siphon problem; a leak in the display is a crack or a seam.

4. Lower the water below the leak, into clean buckets.

Keep this water: it is matched for salinity and temperature, so the livestock can go back into it.

5. If the tank must be drained, move fish and corals into buckets with a heater and an air stone.

They can live for a while in tank water with air and heat while you sort the tank.

Once the tank is stable, what next?

1. Dry and check every plug, socket and extension lead before using them again.
2. Photograph the damage for any insurance claim. Home policies rarely cover livestock (our reading; check your policy).
3. Do not refill a cracked or failing seam: move the livestock to a spare tank or ask a local shop to hold them.

How do I stop it happening again?

• Put every aquarium circuit on an RCD (residual current device), standard UK advice for water and electricity.
• Fit drip loops on every cable so water runs off before the plug.
• Leak detectors under the sump and tank, ideally linked to a controller that stops pumps (BRS).
• Test the sump: switch the return off and check the water that drains back fits without overflowing.

Last checked 21 October 2026. How we check