Algae or Dust?

[bam0271]

Hello,
I turned my pump & filter off for two days. An above ground pool, round, 17,200 gal, liquid chlorine, sand filter, 1.5 hp pump. For these two days I have not seen any reoccurrence of what I thought was algae. Nothing in the usual places or spots. Does this mean it is just dust and dirt and not algae? If it is dust and dirt; why isn't the filter taking it out? If it is algae; why it is not showing up when the pump is turned off?
Thanks for any opinions.
BAM

 

[HermanTX]

The best way to determine if algae is present, is to do an Overnight Chlorine Loss Test
Keep the pump running but do not add chlorine after you do the test in the evening.

 

[HermanTX]

why it is not showing up when the pump is turned off?
Thanks for any opinions.

Algae is only present when your FC levels are low. Even when the pump is off. I have gone 3 days without a pump due to electrical outage and never had algae issue because I kept my FC level at proper level by brushing the pool once I added the LC.
If the FC levels are sufficient, it will keep algae away
Please post values for following
FC
CC
CYA
pH
Thanks.