They both can etch the acrylic surface if your spa. Notice I said "can" not will. Also, the liquid being heavier than the water will settle and be drawn directly into the pumps when activated causing premature failure. Yeah, I know, you will only add it with the jets on. For the first 6 months to a year. After that, you'll think to hell with it I gotta get to work and just toss the stuff in. Eliminate that eventuality and use the prescribed chemicals.
