adding magnesium

Now that everyone is here, I couldn't find anything related but I am having so much trouble with Mg and Calcium dosing, I have IO Reef Crystals, I mixed 5 gallon with 3 cups of salt. Waited 1-2 hours and couldnt get any readings from the salt. I waited +24 hours and I got around 1300-1350 mg. My...

We have a 75 gallon tank with a Fluval 407 cannister filter. Bottom tray-black sponge followed by polyfill, Second tray- Chemi-pure & polyfill. Third level- biomedia. Final tray- ZeoCarb & phosphate remover pads Return line has a fluval spray bar, the Inlet has a Fluval skimmer with midline...