It's pretty common to waste a LOT of chemicals fighting algae. The bottom line is -- if you don't put enough in to kill it, you probably wasted everything you put in. Algae and slime doesn't actually eat chlorine, but it uses it up. Essentially, in any given 24 - 48 hr period, either the algae loses, or you lose all the chemicals you added!
Your pool has a PF of 9, and bleach is about $3/gal, so assuming you've purchased and used $150/3 or 50 gallons of bleach, you have added 50 x 0.5 (lbs Cl2 per gallon) x 9 = 225 ppm of bleach. If you'd added even 1/3 of that within a single 48 hour period, your algae would be gone.
One possible alternative explanation: you've been buying stale or low % bleach. Discount 6% bleach, that's been stored in a warehouse for a year may be 1% bleach + salt. And, some discount stores are selling low % bleach. That's one reason we often recommend Walmart store brand bleach: it's fresh, it's 6%, and it's plain, with none of the pool-un-friendly goop Clorox has been adding to their branded bleach.
Another alternative explanation: you have zero CYA, have added bleach in the MORNING, have fairly clear water in spite of the algae, and have had sunny days. In clear water, on a sunny day, with no CYA, you can lose 95% of what you put in -- no matter how much you put in! That's why we tell people to dose for bleach in the EVENING.
Post your ACTUAL current test results from an OTO & phenol red testkit. If you've added 12 gallons of 6% bleach, and it's not all gone, your chlorine level will be above what the kit will show, but tell me what color it is (dark yellow, orange-yellow, orange, brown).
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