OK well IO can have Mg levels between 900-1100ppm so you might be ok there.
You might want to look into dosing Ca, Mg and an alk buffer now that you have a clam in there using some of that up. I'd do this after you get your water parameters fully tested so you have a baseline.
You might want to put another powerhead in there, or just readjust the ones you have to change up the flow some
