A Housing Board flat owner who converted the doorstep of his property into a fish tank for his koi fish has been asked to remove the unusual structure.

The Tampines Street 41 resident had enclosed the area surrounding the steps up to his ground-floor unit to form a glass tank housing around a dozen pet fish, but was not aware that he needed permission to make the alteration.

Belatedly, the man asked the Tampines Town Council for a permit, and last August, Tampines GRC MP Baey Yam Keng told The Straits Times that the "creative" tank was likely to be allowed, as long as it was found to be structurally sound and safe.

However, HDB said yesterday that the tank would have to be removed, as its position - along a common corridor - poses safety concerns that "could potentially lead to injuries or fatalities".

A spokesman said: "The flat owner has fundamentally altered the entrance steps into a koi tank, which poses several safety issues.

"For instance, the koi tank is made of glass and can shatter on impact. As it is also not enclosed at the top, unsupervised children may climb or fall into the tank."

Electrical sockets and cables connected to the tank are exposed to weather elements, posing further safety concerns, HDB said.

It added that its guiding principle for town councils in managing the use of public spaces is that safety must not be compromised.

The flat's fish-loving residents also own the adjacent flat, through which they enter the unit with the blocked-off doorstep.

Last August, neighbours told The Straits Times that the tank was installed around three years earlier, and one resident described it as "unique and nice".

When ST visited the unit last night, the owner, who declined to give his name, was adamant that the space was his private landing and that he should be allowed to keep the tank.

"It doesn't cause any obstruction to people and the laws should be applied on a case-by-case basis," he said. "If I go to any other unit, I will also find laws broken, such as plants on the stairs."

He said the tank has helped bring the community together, with visitors coming from as far as Jurong and Bukit Batok to view it.

"If I start a petition (to keep the tank), I think people will surely sign it," the owner added.

He had kept koi in normal tanks in the past, but as they grew bigger, he decided to build the tank on the steps. A contractor friend helped him to build it about two to three years ago.

To strengthen the tank, he subsequently used a metal bracket to line its edge. The tank contains more than 50 litres of water and about eight or nine Japanese koi, or carp.

He does not keep any fish in the flat itself, preferring to have them outdoors. He said: "The sun helps the koi develop brighter colours."