The issue is, will it still be good next week?

Products like Pool Magnet Plus *temporarily* hold metals in solution in the water. That's helpful, but the metal is all still there.

However, if you do not shock the pool, but gradually raise chlorine levels AND operate your filter 24/7, there's a good chance, that as the Pool Magnet (HEDP?) breaks down, the metals will be caught by the filter BEFORE they cause problems in the pool.

I found two MSDS sheets for the product. Interestingly, they show two DIFFERENT formulations:
http://www.inlandreno.com/oldsite/pdf/m140003300.pdf (27% HEDP in 1997)
http://www.norflowinc.com/images/Bio...agnet_Plus.pdf (36% HEDP in 2002)

You might note that HEDP is a phosphorous compound AND the products also contain 1 - 2% phosphoric acid. So, their use will add phosphates to your water. This is not necessarily a problem, but many dealers will try to sell you phosphate removers, whether you need them or not.