Same thing happens to me. After I water the plants, perlite looks nice and shiny white, but after a few days it looks a dull yellowish color until I water again. Plants don't seem to mind so I haven't thought anything of it. Oh ya, I add 2 tbps of h2o2/5 gallons, if that means anything to ya.
Sk8orDie Reviewed by Sk8orDie on . Perlite turning yellow!? HELP! Hi guys, I just took out my 4' florecents and put in a 400 watt MH. A good part of my mix is made from perlite and is now turning yellow on the surface. Plants are 16" away from the bulb and it is NOT hot to the hand. Is the bulb to close to the plants? Don't want to burn them. Oh, I transplanted the plants last night into 2 gal containers. Is this normal for the perlite to change yellow? I think the lights are to close...I dono. Room is well vented and is around 80 degrees. Rating: 5