I've never tried TM Pro Reef salt. I use Seachem Reef Salt, which has non-borate alk of 8 dhk (borate levels artificially inflate its dhk readings to 9-10 dhk but the borate is not usable by corals).
What kind of readings are you getting for CA and Alk? I switched to Seachem Reef from IO but my Ca is off the charts and the Alk comes in around 6.2ish dKh.
I will probably go back to IO
I also used Tropic Marin for a while but was not happy with the fact that it had detectable nitrates AND it is now $60 for a 200G bucket...
What test kit do you use to measure calcium? I'm surprised that you are getting a reading of only 440-460 Ca. Typically this salt measures 560-580 Ca at 1.026 salinity....
If those are accurate numbers thats not bad. I used Oceanic when I first started up. Calcium was off the chart and Alk was low. The last bucket of IO I mixed up tested at around 390 calcium, a lil low but not too bad.