Hydroguard isn’t made too far from me so I can find it just about anywhere in town, even the Ace down the street has it. I’ve actually been looking into some of their other products they carry for future grows, specifically two called Rhizo Blast and Silica Blast. I hear a lot of hydro people having success with a silica supplement on here.
MC has silica already. you can add more but dosing is different with mc than other lines. there are a few using it but most on MC don't bother.