Quick answer
Treat an active aquarium leak as both a water and electrical emergency. Keep people away from wet electrical equipment, isolate power from a safe dry location if you can do so without approaching water or exposed electrics, and do not reach into a wet power board. Then lower the water level below the leak if the tank remains stable, transfer livestock to a heated/aerated holding container as needed, and protect the biological filter. A leaking structural seam or cracked panel should not be trusted as a loaded repair.
Protect people before the floor or fish
Water can spread farther than it first appears and may reach power boards, plugs, heaters or extension leads. SafeWork SA treats moisture as an electrical hazard and advises that unsafe equipment be isolated and not re-energised until assessed. If you cannot safely isolate power from a dry location, keep clear and get qualified help.
Do not grab a wet plug, power board or metal aquarium stand while trying to stop the leak. If there is smoke, arcing, a shock, a hot smell or a tripped circuit that will not stay reset, treat the electrical fault as the priority.
Find whether the leak is external plumbing or the aquarium itself
Dry the outside carefully and inspect hoses, canister fittings, overflows, sump return lines and condensation before assuming the glass tank has failed. A loose hose can create litres of water on the floor while the tank itself remains intact. Stop external pumps if doing so is electrically safe and watch whether the leak continues.
If water is coming through a glass crack or structural silicone seam, reduce the load and plan a transfer. Cosmetic wiping or adding sealant to a wet loaded seam is not a reliable structural repair.
Lower load without destabilising the tank
If the panel is still stable and power is safe, remove water to below the leak while preparing containers for livestock. Do not lean on cracked glass or move a partly full aquarium; moving a loaded tank can increase stress on panels and seams. Keep children and pets away from the area.
Use clean food-safe tubs or spare aquariums for fish. Match temperature and salinity where relevant and provide aeration. Move established filter media so it stays wet and oxygenated if the main filter cannot continue safely.
Preserve livestock and biological filtration
A temporary holding system needs oxygen first, then temperature control appropriate to the species, secure covers for jumpers and ammonia monitoring. High stocking in small tubs can overwhelm filtration quickly. Reduce feeding and use conditioned water changes while the permanent tank is unavailable.
Do not place an electric heater in a damaged or leaking container. Use only equipment designed for aquatic use and keep plugs, controllers and connections dry.
Decide whether the tank should be retired
Manufacturer guidance warns against filling glass aquariums with cracks and against modifying or attempting unauthorised repairs under warranty. A structural crack, separated seam, moving brace or panel distortion is a strong reason to retire or professionally assess the aquarium rather than trusting a cosmetic patch.
After cleanup, have water-affected electrical equipment inspected or replaced as appropriate before use. Fix the stand, levelling or support problem that may have contributed to the failure before installing another tank.
Plan the holding system before the next leak
Keep at least one clean food-safe tub, spare airline and battery air pump or other safe emergency aeration option available if you run a large aquarium. A leak is easier to manage when the livestock container already exists and you are not searching for a detergent bucket while water approaches electrical equipment.
After the immediate event, inspect flooring and furniture for trapped water. Swollen particleboard stands and wet power strips may remain unsafe even after the visible puddle is gone. Do not refill the repaired or replacement tank until its support is dry, level and structurally sound.
Record where the leak started. Hose fittings, bulkheads, rim damage and seam failures have different preventive fixes. Treating every event as “the tank leaked” misses the maintenance lesson that can prevent the next one.
If the leak rate increases as water level remains above a particular seam or fitting, that observation can help locate the source, but do not keep a structurally suspect aquarium full just to diagnose it. Once people and power are safe, lower the water to a level that stops or substantially reduces the leak and move livestock if necessary. Use towels and containers to control spread, but treat them as damage-control tools, not structural repairs. A temporary reduction in leaking does not make a cracked panel or separating seam safe to refill.
Research and review
This is original AquaNexus writing prepared for practical aquarium use. The husbandry, identification and safety framework was checked against the references below. Source wording, tables and images were not copied into this guide.
Water and mains electricity can be fatal. If a leak has reached electrical equipment or you cannot safely isolate power from a dry location, keep clear and use a licensed electrician or emergency service as appropriate.