One problem (a couple actually) - most of the scented bleaches contain detergents as well as the 'scent'. Was it one of the 'non-splash' varieties? if so they definitely have chemicals you dont want in your tank. Muriatic acid will PROBABLY not have any effect on detergents in the water - so I'm not sure why you would want to use it. Frankly - if indeed the bleach you used contained detergents - IMHO you should not use the rock - as painful as that probably would be. Prime will have no effect on the detergent either. All you would need for the bleach part is 'chlorine neutralizer' (sodium thiosulfate) - rather than prime (its cheaper).
You need to be EXTREMELY careful using muriatic acid in the first place (its nasty stuff) FYI - and mixed with bleach it releases Chlorine gas - So this is definitely an outdoor project (if you decide to use it). in fact - just breathing in the gas from regular strength muriatic acid is toxic.
(If you use it - follow the dilution instructions carefully - if you pour it into water too quickly - it can boil and splatter - and cause burns). There are also lots of 'local laws' of how it needs to be disposed of (i.e. you cant dump in down the drain, toilet, onto the ground, etc).
Here is a good summary: Mixing bleach, or sodium hypochlorite with muriatic acid will liberate chlorine gas, which is definitely toxic, and a severe irritant to eyes and nasal passages and the lungs even in small amounts. ... The acid is strong if breathed in but is deadly if mixed with chlorine.