In 1998, fish farmers in Ma Wan protected their stocks by turning back toxic red tides using the motors of their sampans. The blooms we have seen in Hong Kong waters over the past two weeks have been of a less harmful variety, as luck would have it. But the outbreaks are a timely reminder of how urgent the task of cleaning up our harbour really is. If the conditions are ripe for less harmful algae to flourish, there is every risk that the next outbreak in our waters could be less benign. The conditions and water flow behind this month's red tides - including the unseasonably cool weather, which has provided ideal temperatures for the algae to grow - may be beyond our control. Nonetheless, one of the factors behind the phenomenon most certainly is something we can influence, and that is the presence of nitrogen and phosphorous on which the blooms feed. The main source of these nutrients is the 2.6 million cubic metres of sewage that makes its way, some treated, some untreated, into our waters each day. The progress in reducing nitrogen and phosphorous levels has been remarkable since the first phase of the Harbour Area Treatment Scheme was implemented in 2001: they have dropped by 16 per cent and 36 per cent respectively. But progress is not being made quickly enough, if these outbreaks are anything to go by. Over the past five years, Hong Kong has seen an annual average of 31 red-tide incidents. This year, we are on track to hit this average, with 27 incidents so far. The government should be commended for wanting to move forward with the second stage of the treatment scheme, which will see all sewage chemically treated before disposal, and for proposing biological treatment, which should further reduce nitrogen and phosphorous levels in the sea. The flaw in the plan, though, is a drawn-out timetable that provides for construction to begin only in 2007-2008 and end in 2013-2014. And that is just for the treatment works; there is no timetable at all in the proposal for implementing biological treatment. Granted, there is some controversy over biological treatment: will it be effective enough to warrant the $11 billion price tag? But that is no reason to drag out the impact studies and the inevitable debate on whether or not to proceed. Let the information be brought to the public as soon as possible so that society can make an informed decision. Meanwhile, there must be a way to speed up construction of the chemical treatment works, the need for which is not in doubt. Our red tide problem has thus far been more inconvenient than hazardous. This may not remain the case indefinitely. Even if part of the problem is pollution from Guangdong, Hong Kong has to play its part in reducing the risk of red tides. The best way to do this is by cleaning up the harbour - and doing it sooner rather than later.