Just pulled cover off.. green swamp water

[Watermom]

Instead of bagged shock, is it better to use bleach?

Depends on what your water testing readings are. I personally just use bleach for shocking and for daily chlorination, but if your CYA is low enough, you can shock with dichlor.

If so, what's the ratio, one bag of shock = 1/2 gallon of bleach?

Dunno. Plus, there are many types of bags of shock of various sizes.