The plankton bloom which wiped out more than 500 tonnes of fish along the East Johor Strait last week, and seems to have now affected farms in the western side, has raised concerns on the industry's future here.
Affected farmers told The Straits Times that despite earlier warnings given by the Agri-Food and Veterinary Authority (AVA), they were shocked at how sudden and severe the latest bloom was.
Mr Simon Ho, who is in his 60s and has been in the business for five years, had put in oxygen compressors since receiving the warnings in the middle of last month. But he still lost all 35 tonnes of his fish- the product of more than a year's worth of work - at his farm off Lorong Halus jetty.
In January and February last year, thousands of fish died after being poisoned by plankton blooms caused by high temperatures and low tides.
But Mr Frank Tan, 40, who owns Marine Life Aquaculture, said that unlike last year, the bloom was much harder to detect this time.
The bloom typically turns water brownish-red, when the plankton appear in large numbers. This year, he did not see this happening.
Some fish farmers say their enterprise is a "high risk" one, given that they already have to cope with unpredictable environmental factors, such as temperature.
Of Singapore's 126 fish farms, 117 are coastal, and most grow their fish in net cages in the sea. That means the livestock is vulnerable to changes in the environment.
Now the worry is that the deadly plankton blooms may become an annual affair.
The answer may be to rear the fish in a closed containment aquaculture system, which will shield the animals from external factors.
These systems include putting the fish in giant tanks into which filtered and oxygenated seawater is pumped. These tanks can be placed on land or on platforms out at sea.
But older farmers are reluctant to make the change from the farming methods they grew up with and know so well, while others say containment systems simply cost too much.
Mr Ong Kim Pit, who is 65 and has been in the business for about 20 years, said: "It's not that easy. The containers can only rear so much fish and you need to spend thousands building them."
Still, there are those willing to take the plunge, with the help of the Government, which is encouraging greater local fish production to boost the country's food security. In 2013, 8 per cent of fish supply here came from local sources, and the plan is to increase this to 15 per cent.
Last August, the Ministry of National Development rolled out a $63 million Agriculture Productivity Fund to help local farmers boost their yields and raise productivity.
The AVA also this month awarded a tender to develop closed fish rearing systems to five companies.
One of them is The Fish Farmer, which produces 800 tonnes of fish annually at its Lim Chu Kang and Changi farms.
Chief executive Malcolm Ong, 51, hopes to grow his fish fry, which are more vulnerable to disease and the bloom, in tanks in about six months' time.
The system is estimated to cost $364,000, and AVA will reimburse some of the cost, he said.
Once the fish grow big enough, he will transfer them to net cages.
"I am really committed to finding a solution," said Mr Ong. "I am not going to be defeated by the plankton bloom."