Do you mean your 150 reactor? If you want to run both in a reactor it will be less than optimal but it works. I see 2 issues: flow rates & regeneration. If imagine though that Purigen & GFO
both need slow flow rates which might not be too bad. Purigen is easily renewed with bleach, with GFO
in there you couldn't do that anymore.
If you mean running them separately, but at the same time, go for it. Start small with the GFO
(1/2 recommended dose) and work up as you can shock any coral by dropping phosphates too quickly.