Okay, I'll try to sort this out for you.
A high pressure air tank can be used on your SLG, and pretty much any paintball marker.
EXCEPT (and someone correct me if I'm wrong) - there is (was?) an Angel branded marker that REQUIRED a low pressure air tank, it couldn't handle a high pressure tank.
But as everyone said, the high pressure tank will work fine.
The general theory is this...
High pressure into a marker = less volume of air.
Low pressure into a marker = more volume of air.
Overall you use the "same" amount of air regardless of which type of tank you use.
Here's ANOTHER but...
Not all low pressure tanks can keep up a sustainted rate of fire, and you may experiance drop off, spluttering etc, so the high pressure tank is really the better choice.
That, and you might get lumbered with a good old fashioned Tippy as a backup, and those suckers DO require 800-something psi...