having possible mustard algae problem 3 weeks now

[PoolDoc]

1. Go buy a cheap OTO/phenol red drops kit. Use it to maintain your chlorine level in the DARK yellow to orange range.

2. Tell us your pool dimensions, so we can figure doses.

3. Order a K2006 kit, so we can get accurate test results => http://pool9.net/tk/
Before you use it, watch the videos:

http://pool9.net/tk-guide/
http://pool9.net/tk-interfere/

We call test strips 'guess-strips' for a reason, and the CYA measurements are especially inaccurate.

4. Low phosphate levels aren't essential for algae control, but WILL enable you to eradicate it more quickly, and more easily avoid it in the future. BUT, it will probably cost you $100 more, and will require another kit and monitoring another factor. If the money doesn't bother you, get the Taylor phosphate kit when you order the K2006. 4 quarts of the Kem-Tek product should be enough for most IG pools at typical phosphate levels:
Kem-Tek 265-6 Pool and Spa Phosphate Remover, 1 Quart
But, be sure you understand: CHLORINE kills the algae; low phosphates just makes it easier to kill.

5. Read the Cl-CYA page -- it's essential for you to understand that your correct chlorine level is determined by your CYA level:
http://pool9.net/cl-cya/

Good luck!