you could use purple up, lots of products on the market.
BUT you have to be careful when dosing, if you dose too much of anything you could throw off everything else, ph, alk, etc.
When i dose i ctually do a half dose test for a couple of days then do another half dose.
My coraline is all kinds of colors pink, red, green, etc. heres a pic for an example.
Most of my rock is only a couple of months old but some of it did come from a teardown.
I test for the following and dose only as needed and try to keep my ca ~450.
I just started testing for mag and phos, best advise i can give you is read, read, read then read some more! (water chem)
trate
alk
ca
mag
phos
ph