While we cannot tell you how much of anything to add just yet, it's a good bet that you don't have enough chlorine in your pool. Without knowing the level of your CYA (stabilizer), it would be a shot in the dark. CYA level determines the ideal level to "shock" your pool (raise chlorine levels really high to kill everything in it), and the maintenance level (what you need to keep your pool sanitary).

Just so you know: 1 gallon of 6% bleach will add between 15 and 18ppm of chlorine to your pool. And you MAY have to add that much.

But I'm guessing you've been using Di-Chlor powdered chlorine and have been trying to keep the chlorine level at "3" which, on every little test kit says is the "good" level. Been there, done that. "3" is NOT the right level...but I'm getting ahead of myself.

If you need to take a sample to a pool store, go ahead but don't buy anything, especially not calcium or algaecides. No matter WHAT they say calcium will do NOTHING for your pool, and algaecides will make it much, much worse. Again, been there.....

Carl