Even under ideal conditions that Jason points out, the reproduction or generation rate (i.e. the time it takes for the population to double in size) for algae is from 3 to 8 hours. This is why the water always turns dull and then cloudy before it turns green (for standard free-floating green algae). However, long before the water even gets dull looking (i.e. not crystal clear) the growth of algae can consume lots of chlorine in the sense that chlorine tries to kill it and there's a lot there even before it starts becoming visible.
Typically, if you completely let a pool go down to zero chlorine then the algae won't start to be visible for a 2-3 days (perhaps a little dull after 1 day) unless the algae was already just below being visible and on the edge of a bloom with the chlorine just barely holding it back.
This is in contrast to bacterial growth where the generation time is around 15 to 60 minutes and is why it is critically important not to let the chlorine drop to zero even for a short time. A pool can look perfectly fine but be teaming with bacteria, some of which may be harmful if swallowed (fecal bacteria, usually).
Richard
Typically, if you completely let a pool go down to zero chlorine then the algae won't start to be visible for a 2-3 days (perhaps a little dull after 1 day) unless the algae was already just below being visible and on the edge of a bloom with the chlorine just barely holding it back.
This is in contrast to bacterial growth where the generation time is around 15 to 60 minutes and is why it is critically important not to let the chlorine drop to zero even for a short time. A pool can look perfectly fine but be teaming with bacteria, some of which may be harmful if swallowed (fecal bacteria, usually).
Richard