Greetings from a newbie in Middle Tennessee!

[Royal]

Welcome! This is a very friendly place, and I'm sure you'll get a ton of help. I'm no expert, but I'll pitch in a little.

You don't NEED any one medium. I've never heard of 'blue rock' but it may be great. Maybe it's a brand name? Anyway, the right medium for you may be different than what works for others. I'd suggest a bark mix like Better-Gro (found at Lowe's and Sprawl Mart). I like Farfard's mix too - it's just a bark mix with coconut husk chips in there too. I've had mixed results with Shultz brand stuff.

Keep it in a pot that seems a little small for the plant. Dendrobium roots like being crowded. When you water, drench it completely. Let it get mostly dry, then drench it again. In nature they grow on trees, so the roots need to dry quickly. Bark medium will take care of this.

Have fun around here! Kiki is right, do a little digging and you'll find more info than you even knew was out there - I did.