ALGAE - prevention and cure

Any thing to do with swimming pools, fish ponds, or other man made structures which hold water (but not wells for drinking water).

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ALGAE - prevention and cure

Postby jazzman » Wed Sep 24, 2008 5:22 pm

Are you having problems with algae in your pool?
It's that time of the year - hot and humid, and spores scattered by wind and rain. If your pool is being regularly and correctly maintained, you should not be having any problems, but to judge by the number of PMs I"ve had recently on the subject, not everyone is so lucky.

As I've mentioned before, I really can't reply personally to such a deluge of messages so here are some tips how to control and combat it:

Algae blooms are a problem best avoided and maintaining proper water quality and frequent brushing of pool walls will deprive algae of the opportunity to get started. If your pool has been empty for quite a while, or if you are starting a new pool for the first time, thorough cleaning of the tiles and grout, and algae pre-treatment are good preventatives. Using a pressure washer is a good idea, but don't use it so hard that you drive the grout out from between the tiles.
Algae can grow in swimming pools if nutrients are present and a sufficient level of free chlorine is not maintained. In addition to properly dosing your water, it is recommended that the algaecide be added in the morning on a bright sunny day for best results. Algae are plants and grow in the presence of sunlight. Adding algaecide during algae's best growth time will increase intake of the algaecide and make it more effective.
Below are descriptions of the three most common algae problems in swimming pools.

Green Algae The most common algae floats in the water and on the surface. Left unchecked, green algae will propagate extremely quickly. This is less frequent in Thailand, but one direct hit from a flash of lightning can turn your pool into pea soup overnight.

Mustard Algae
settles on pool walls and causes a slimy yellow film. Again, this this is less frequent in Thailand, but for some off reason it seems to appear more often in highly built up city areas and heavily used commercial pools.

BLACK ALGAE appears in furry "buds" or clumps attached to tile grout, corners, steps and pool surfaces. It looks a bit like some forms of mould. It is the main problem here in Thailand, and sod's law willhave it that it is also the most difficult one to get rid of.


Remember that shock, or super chlorination can never do much harm, but the bathing experience will be unpleasant until the chlorine drops to its normal level. Under normal conditions, there should be NO apparent odour of chlorine; if your pool smells of chlorine, this is due to the chlorine that is combined with other stuff and cannot escape - it actually means that there is not enough free chlorine in the pool.

Green Algae - is very susceptible to chemical treatment. Superchlorinate with 10 to 20 ppm chlorine in the evening. Keep the filter running and brush the pool walls and bottom. Periodically check chlorine and maintain above 3 ppm until water clears. Using an algeicide containing quaternary ammonia the next morning will help prevent the return of green algae.

Mustard Algae - is much more resistant to chemical treatment and clings more tightly to pool walls than green algae. Adjust pH and superchlorinate as for green algae then brush carefully. Later vacuum the pool, check chlorine and superchorinate again if necessary. Mustard algae will generally return unless treated with a special mustard algicide or a copper based (CuSo4) algicide. Algicide should be added in the morning to treat algae in daylight - its most active period.

BLACK ALGAE - can be controlled to some extent by frequent superchlorination and careful brushing with a stiff brush. (You should have a wire-brush attachment for your telescopic pole). Spot treatments can be made by turning off the recirculation pumps and pouring granular chlorine directly on recently brushed spots. Trichlor tablets can also be rubbed on recently brushed areas to spot treat. You need to usef strong algicides and maintenance of relatively high free-chlorine residual, but complete removal of black algae may require draining and cleaning the pool.

There are some proprietary products such as Swimtrine®, and Pooltrine® available in most pool shops in Bangkok, Pattaya, and Phuket, but they are horrendously expensive (luxury goods price tag for pool owners) at nearly 2,000 baht for a 2.4 litre bottle. Although it is highly concentrated, the tendency is always to overdose, and your money is quickly used up. As mentioned before, good pool hygiene ids the best remedy, but you can always try first by using plain Copper Sulphate (CuSo4) crystals dissolved in water. You can obtain this from a chemicals supplier quite cheaply. *
Potassium Tetraborate:
This chemical, when added to the pool water in proper dosage, prevents algae from converting carbon dioxide into the fuel it needs for growth. It"s quite effective.

Another item to look at is the method of sanitation and the type of filtering you have. Far too many pools out there were sold with marginal filter systems, meant to run 24 hrs per day. Well, these systems get old and tired, or the new owners only run it 12 hrs per day (or less). For good algae prevention, you need a combination of good filtration, sanitation and circulation. Not many of us here in n Thailand have had pools long enough to justify changing the equipment, but I have known failures of cheap or underpowered pumps and filters after as little as two years. It may be time to consider changing the old pump and filter. It's cheaper and easier to pay a little up front for more chemicals, electricity or better equipment than all the money and aggravation spent on fighting algae blooms

You'll notice from my other posts that I am a strong protagonist for salt water chlorinators. The ROI is rapid, and you will have fully automatic, optimal chlorination, and you will rarely need to purchase anty additional chemicals; by-products of the eletroysis are also those that work well as algaecides.

Good luck! And don't hesitate to post your experience here.
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Don't let this happen in YOUR house.
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Re: ALGAE - prevention and cure

Postby jazzman » Mon Dec 21, 2009 10:56 am

The same proprietary products such as Pooltrine®, etc., costing 1,800 - 2,200 per bottle, etc are now available at reasonable prices for as little as 990 baht per bottle, but you need to shop around for them. see other threads on this forum for chemical supplies.
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