CLR vs. Muriatic acid to remove hard water scale?

[bradleyheathhays]

Recently acquired a used tank with an unidentified white scale on the sides that I'm trying to remove. Turned the tank on it's front side and soaked the scale for a week with 100% vinegar and it still didn't scrub off. Was given advice to soak a small spot with either CLR or muriatic acid to determine if it was actually water scale, or if it was glass etching for which nothing can be done. Thankfully a small patch soaked with CLR for 2 hours has scrubbed away!...which means what I'm dealing with is probably just water scale.

So, my question is...which should I used to get the rest of this scale off...CLR or muriatic acid? I'm guessing the muriatic, because after rinsing, if the residue shows up in my filled tank water I can just adjust by using pH+ or -.

Thanks

 

[aqua_chem]

The major component of muratic acid is HCl, and is extremely water soluble, meaning it can easily be cleaned off just by rinsing. CLR, on the other hand, I have no idea about. I probably wouldn't trust it.

 

[adeebm]

Yeah, you probably don't want what's left by CLR in a fishtank. For ease of cleaning, go with the muriatic acid.

--Adeeb