Pool store Liquid chlorine at 12.5% Sodium Hypochlorite or household bleach at 6% Sodium Hypochlorite?

Looking over your post, I'm not sure if you have no chlorine or lots of chlorine as DPD and strips can bleach out in high chlorine. If you really have no chlorine then you probably have ammonia and I'll reccommend that you start going after it with lots of chlorine. But, if your chlorine is actually high, we'll need to figure out why you still have algae.

An OTO chlorine test will clearly tell us if you have no chlorine or really high chlorine. OTO/pH tests are widely available, pick one up before we go on.
If the Walmart's in your area have the HTH 6-way kit, get one. (Check availability) It has OTO, a better than average pH test, and other necessary tests

At a CYA level of 30, your shock level is 15 according to Ben's Best Guess Chart.
12 gallons of 6% bleach should put 32 ppm FC in your pool - probably too much but, a good amount to buy.
12 gallons of 12.5% LC should add 65ppm FC - Too much.

If OTO shows you have no chlorine, add 6 gallons of 6% or 3 gallons of 12.5%.

Please get the OTO and let us know if the test is clear (0) or Dark yellow, orange red, brown.