Hi, and thanks for the great forum. I've been reading for several weeks and finally decided to register and ask a question.

I recently converted to BBB after 7-8 years of using stupidly-expensive BioGuard shock and smartsticks. As a result, my CYA is quite high... dip sticks read right at 100; the pool store tested at 91; and my recently-acquired Taylor K2006 kit reads well over 100.

I immediately took the FC up to about 10, and I'm losing about 2ppm per day, but it holds fine overnight. I had been keeping it in the 3-5 range previously.

The water looks fine, except that I have a recurring problem with what I think is the dreaded yellow/mustard algae. I've had a minor problem with this for 2-3 years in late summer. It appears on all flat surfaces and the wall of the shady side. It's a very fine brown/yellow dust that - when brushed - "poofs" into a cloud that looks brown/yellow/greenish, but very quickly disappears. Then, 2-3 days later, it's back on all flat surfaces and the shady walls, and other places with poor circulation.

All this time, I convinced myself it was just some fine dirt or pollen that wasn't being filtered by my cartridge filter. But after reading extensively here, I'm convinced it is the hard-to-kill yellow/mustard beast. I can't imagine that dirt would attach itself to vertical surfaces. There's not a ton of the stuff (very spotty), and it does go away with cooler weather.

Problem is: with my CYA so high, I would need to add an insane amount of bleach to kill this stuff. The best guess chart says 75-100 ppm of FC. Are you guys really recommending that??

I have a cartridge filter, so I get very little (if any) water loss in the normal course of operating the pool. This is probably why the CYA has built up so high. But also, I have no way to vacuum the stuff to waste. It's an IG gunite pool, but I'm not too comfortable with taking half the water out.

I would welcome any and all suggestions. Thanks. I listed my equipment and other test results below.

35X20 (approx), IG gunite, 18k gal, pebbletec plaster
Pentair cartridge filter, 2.0 HP pump

FC=10
CC=0
CYA=>100
pH=7.6
TA=105
Borates=40