Lime Scale Buildup in Pump ?

[DiverDude]

Anyone else having issues with lime scale buildup in their pumps ?

The MaxiJet 1200 in my HOB skimmer seized again last night (this is with a new impeller) for the second time in 2 months.

Scrape or dissolve the buildup and she runs great for another month. This is a new issue. Water chemistry numbers are mostly where they should be (a little low on Mg (~1100) and pH is at 8.1. Water is all RO/DI and I'm using Reef Crystals (1.026).