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This may be biofilm. If you want to make sure you get rid of it, go out and get some bleach. Use 4 or 5 gallons. Open all the air controls (if there are any) and put any diverters in the middle. Put all the bleach in and run all the jets for 5-10 minutes. Then shut all the pumps off. Do this 3 or 4 times and then drain the spa. This should not only kill any bacteria in there, it should also burn it right up. Just make sure you don't leave the water in the tub for much more than an hour as you are getting the ppm of chlorine into the 100-200 range.
The objective is to get the chlorine level up to 100 ppm.If you do not kill it it will return (in theory).
Your in S. Ont any of the pool & spa stores will have it in a 900g container or 30gram packages. Just ask for granular chlorine unstablized.
WOW long day.
Where did the number 100ppm come from and where have you read that? I agree that large amounts of chlroine is required to kill this type of algea but 100ppm is totally over the top. Would 25ppm not kill it? 20ppm... 40ppm...? You bet it would!I too would not recommend liquid bleach as chlorine in a granular form (dichlor) has a more sustained ability to kill. Make sure anything that has been in that water also gets treated (ie toys, floater, etc.)Steve