A leaking fish tank led to a lot of damage for this downstairs apartment owner.

Water damage can be hard to repair, as this apartment-owner found out.

The apartment was destroyed by an over-flowing fish tank in the apartment above.

A buyer could score a bargain: this apartment, which once sold for $1.85m, is going to auction starting at $550k.

A once-decadent apartment in Oriental Bay has been gutted after an unfortunate case of an overflowing fish tank.

The swanky beachside apartment, which previously sold for $1.85 million, is now due to go to auction starting at $550,000.

The agent says the reason for the massive drop in value isn't lagging house prices: it was fish-tank in the apartment above that overflowed, wrecking the downstairs flat.

CHRIS SKELTON/FAIRFAX NZ The one bedroom apartment at 3/212 Oriental Parade, Oriental Bay in Wellington once sold for $1.85 million. Now it's going to auction starting at just $550,000, thanks to a case of an overflowing fish tank upstairs that destroyed the place.

Just Paterson Real Estate agent Charles Morley-Hall said the new owner wouldn't have to worry about rogue fish tanks ruining their new investment.

"This was once one of the most amazing apartments on Oriental Parade with a fit out that would have won awards and an art collection to match," the ad reads.

"Believe it or not a fish tank in the apartment above overflowed and wrecked the apartment below. The good news is that the fish tank is now long gone."

He said he thought it was best to be honest about the fish-tank incident in the apartment's Trade Me ad.

The house was now a blank canvas for someone with a vision to work their magic, he said.

The owner of the property was a high-profile Wellingtonian who did not want to be named, Morley-Hall said.

Registered builder David Barton said he was not surprised the downstairs apartment had to be gutted due to the overflowing tank.

"It would have just absolutely smashed all the gib, all the wood would be wet, all the carpet, the floor would be rotten. Especially if it was a lot of litres of water," he said.

He said he hadn't dealt with a case of fish-tank water damage before, but it was the same as any water-logging.

"It's like anything - it could be a sink or a basin that's constantly flowing, and it depends how long it was leaking for, but the timber could have been rotting, too," he said.

If the tank had held salt water fish, there was a possibility the damage would have been worse.

Hollywood Fish Farm manager Rebecca Buchan said the average size of a fish tank was fairly small, but they could go up to 1000 litres.

The business sold tanks up to 650L capacity, but also took orders for custom-made larger tanks.

"You could potentially make a tank up to whatever size you want if you had the money," she said.

Insurance Council chief executive Tim Grafton said he didn't know how frequently fish tanks spilled their loads, but he had heard of cases of upstairs swimming pools leaking below.

"That wasn't a fish tank but it caused a pretty substantial amount of damage," he said.

Grafton said insurance companies in those cases would be looking to see if it were a sudden, accidental fish tank leak, or a gradual one.

If someone fell on the fish tank, or an object went through it, the owner might be more likely to claim cover.

"If the person below has damage, their insurance company would be looking to provide cover and might look to go for the owner upstairs for causing the damage," he said.

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