Filter Cartridge is green but pool water sparkles, should I worry?

Hi Everyone, I'm a newbie here. Although I've owned an 18 foot above ground pool for 7 years, I'm seeing something for the first time. I have opened my pool about 2 weeks ago (on Long Island, NY). It took the usual 5 days or so to get the chem levels right and all was good. My first couple of weeks I like to clean the filter cartridge once a week after vacuuming. Yesterday I noticed that the cartridge had a pretty green tint that washed off easily with a garden hose. There is not a sign of algae in the pool and the water sparkles. I was wondering if maybe one of the chemicals may cause this, or should i worry that I have some 'invisible' algae? Thanks much for your time.

Mike

What are all the chemicals you have used? Anything with copper in it?

"Should you worry?" Yes.

Green on filters is often either algae (not good) or copper (not good, either). You can find out by getting some bleach, some Vitamin C tabs, a couple of clear wine glasses, and some green sludge off your filter. Put a bit of the sludge in each glass, then add bleach to one. Add tap water + Vit. C to the other. If it's algae, the bleach will turn it brown. If it's copper, the Vit. C will cause the color to disappear or at least change.

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