Walmart bleach is just fine. It is all I have ever used in my pool for the past 8 years. If your cc level is 0.5, I normally say don't worry about it. Except that your pool apparently still has a big chlorine demand. I can't tell you how high you need to shock to without knowing your cya reading. Check the "best guess" chart sticky to know how high to shock to. When your pool quits sucking up so much bleach, you can then go to maintenance levels of FC. Like I said, a CC reading of 0.5 is nothing to worry about.