Lime Scale Buildup in Pump ?

[DiverDude]

ok so I finally had time this morning to do a full load of water tests:

pH: 8.1
NO3: 0
NO4: 0
Ca: 450
Mg: 1050
Alk: 2 meq/l

So, as always, my Mg is low as is Alk. Notice how Ca is a little high.

Ok, so here is the odd bit: I've been supplementing Mg like crazy and Alk as well but no Ca. So I can't get Alk and Mg high enough but Ca is high even with no supplementation.

Tank has good SPS growth but I have a bad HA problem that is ongoing....

Doesn't seem to add up as I *should* be having trouble maintaining Ca, but I don't.