Stubborn algae can't be brushed off

[ti_chris]

I have a spot on my pool that has extremely stubborn algae. I've tried brushing it off with a brush using metal bristles. A solid 50 back/forth strokes didn't do that much sadly. In the past, I was able to brush the algea and it would basically 'dust' off into the pool and would be easy to dislodge from the wall. This is the first time that I'm facing such stubborn algae it simply doesn't respond to brushing. I'm shocking my pool hard and I know this will work from experience. However since the pool has been neglected for 1.5yr, I suspect that it never really fully died and got somehow stuck in the crevice or maybe behind a calcium buildup and although the pool thereafter appears clean, the fact that it's always the same spot that generates algae makes me wonder if there isn't something larger here. And every time it comes back, it's insanely stubborn. The brush is virtually useless.

Am I at the stage where algea is hiding in so many crevices that I'd need an acid wash to fully rid my pool of the stubborn algea?

 

[mknauss]

Post a full set of pool water chemistry test results.
Do you pass an Overnight Chlorine Loss Test?
Algae rarely 'stains'. Typically it is a metal stain.

 

[sande005]

When green and growing well, I sometimes had really stubborn spots. When green, they would stick ferociously. But always, with enough Cl, long enough, they died and became easy to brush off. Local spot environments can vary widely, so a pool can have optimal places for algae to first establish on a surface. A location may also include other creatures (a biofilm) that helps protect the algae from the Cl, and helps it stick more. More brushing, continued high chlorine, and time are the answers. Hence the SLAM method, which introduces the time component along with the others. Yes, it may take days, or even weeks, to completely rid a pool of algae.

 

[ti_chris]

Post a full set of pool water chemistry test results.
Do you pass an Overnight Chlorine Loss Test?
Algae rarely 'stains'. Typically it is a metal stain.

I know for sure that these are algae because it all goes away when I slam the pool. I'm just not used to algae that I can't brush away.
It's fine now that I slammed it, but I find it really odd that that with just a few days of neglect, it grows to a point where I can't brush it off at all.

When green and growing well, I sometimes had really stubborn spots. When green, they would stick ferociously. But always, with enough Cl, long enough, they died and became easy to brush off. Local spot environments can vary widely, so a pool can have optimal places for algae to first establish on a surface. A location may also include other creatures (a biofilm) that helps protect the algae from the Cl, and helps it stick more. More brushing, continued high chlorine, and time are the answers. Hence the SLAM method, which introduces the time component along with the others. Yes, it may take days, or even weeks, to completely rid a pool of algae.

Yah with chlorine alone it all goes away. I don't even need to brush. Brushing alone just doesn't seem to do anything which is really weird. Perhaps there's a little biofilm of some form but I'd still expect the chlorine to kill it.