Dwindling profits from the sale of aquarium fish have forced some major ornamental fish farms here to change tack - they have started cultivating food fish like grouper and plan to do it on a large scale in a few years' time.
One farm even plans to start a live seafood market.
Of the estimated 70 ornamental fish farms here, at least five - Apollo Aquarium, Panda Aquatic Centre, Nippon Koi Farm, Max Koi Farm, and Dreamfish Inc - have embarked on making the change.
The farms use sea water or freshwater recycling systems to rear food fish in concrete inland ponds.
They are helping to boost the output of Singapore's food-fish farms. The country currently produces 8 per cent of the food fish it consumes - a figure that has risen by only four percentage points since 2010 - well short of the 15 per cent target.
The owner of Nippon Koi Farm in Jalan Lekar in Choa Chu Kang, Mr Pay Bok Sing, 53, started rearing food fish in small quantities in 2013. Of his farm's 300 ponds, about 100 of the largest ones now rear fish such as marble gobi and grouper, and prawns.
Demand for the ornamental koi fish, he said, has halved over the past five years. "Few people are breeding koi as a hobby," he told The Straits Times, adding that he now produces 11/2 tonnes to 2 tonnes of fish a month for restaurants and wet markets.
"We figured that the demand for food will always be there; people will always need to eat," he said.
Singapore is still the world's largest exporter of ornamental fish like mollies, guppies, goldfish and koi, but exports have fallen to levels similar to those a decade ago.
The latest UN Comtrade statistics released in May showed that firms here exported about US$56 million (S$76 million) worth of fish in 2013, comparable to the US$54 million worth of fish exported in 2005.
At Max Koi Farm in Neo Tiew Crescent in Lim Chu Kang, food fish now make up 30 per cent of the farm's revenue. Owner Max Ng, 44, started tinkering with food-fish production two years ago because "the tropical fish industry was coming down and an alternative was needed".
He has so far ploughed $3 million into his food-fish business, and plans to go into full-scale commercial farming by year end, and to sell to supermarkets.
Mr Ng believes land-based food-fish farms have an advantage over sea-based ones.
The water used in land-based farms is treated and recirculated in self-contained systems that protect the fish from disease. This lowers mortality rates and allows more fish to be reared in a single tank. The chance of a plankton bloom is also zero, said Mr Ng.
A plankton bloom hit earlier this year, killing some 500 tonnes of fish at farms in Changi, Lim Chu Kang and Pulau Ubin.
Meanwhile, the owner of Panda Aquatic Centre, Mr Kan Tien Siong, 69, has 5,000 jade perch fingerlings in his farm now.
He is targeting the live-fish market in Singapore, and intends to slowly build up demand for the fish, which is eaten as sashimi in some countries.
"This fish has lots of potential," he said, adding that 10 of his 35 ponds now house food fish.
Dreamfish Inc is developing a food-fish farming system and will have 2ha of its 8ha farm devoted to food-fish farming in about two years. When that happens, managing director Nicolas Chia, 44, expects a turnover of about $4 million a year from food-fish rearing.
Apollo Aquarium started rearing shrimp in 2013, and is now growing pilot lines of grouper and coral trout. It plans to become fully commercialised in a year's time.
An Agri-Food and Veterinary Authority (AVA) spokesman said a handful of the estimated 70 ornamental fish farms here are exploring food-fish cultivation and that some have approached the AVA for technical assistance.
"Indoor land-based farming has its advantage of better environmental control," said the spokesman. "However, Singapore has limited land with competing needs. Thus, AVA will continue to work with farmers to intensify agriculture land use, raise productivity and capability."
Fitness trainer Chua Ping Wei, 32, said: "Fish from a tank on land seems better. There is more control over its quality.
"It will also be good if I have somewhere to buy live seafood at good prices."