When 40-year-old Frank Tan first saw signs, in the middle of last month, that a plankton bloom was coming, he tried to save his adult fish by moving them to inland tanks on Pulau Ketam, just opposite his Changi farm.

"I wanted to get three boats to tow our floating net cages, but that didn't work out," said Mr Tan. "The tides and wind were too strong."

The owner of Marine Life Aquaculture ended up losing 120 tonnes of fish in total - the bulk of his stock. He put the loss at $1.2 million.

Now, he is planning to make a permanent move.

In two months, he will move his net cages to either Pulau Tekong or the Southern Islands. The tides are stronger there, which makes it harder for plankton to grow in one place.

The entire process will cost him $500,000.

He set up the company in 2009 after quitting his job as a regional sales manager at an oil and gas firm.

His love for fish runs "in the blood", he said with a smile.

"My grandfather used to run a kelong, my wife came from a family of fishmongers and, these days, whenever my 21/2-year-old daughter goes to a fish shop, she points to the tanks and refuses to leave," he added.

His Pulau Ketam site already houses more than 80 tanks. Seabass and threadfin are kept there until they are about 100 days old, after which they are transferred to net cages.

They are then reared in the open sea until they reach a marketable size - 1.5kg to 2kg.

Mr Tan hopes to build more closed-containment systems eventually, but he said "skill" is needed to make them cost-effective.

For now, he is pinning his hopes on the relocation.

"It's too bad, but we should have moved there earlier," he said.