hard to tell with all the various species out there that are referred to as "medusa pleco" - just from various size reports ranging from five inches to eighteen inches leads me to believe there are several. Check out planetcatfish.com, go through the cat-e-log of common names and see if you can find a photo of one that looks like your particular catfish. that will let you know what you have and you can decide from there whether it's "safe" or not. So far, all the results I've seen would indicate that it's safe, but if you're gonna feed it sinking tablets, you wanna do the carnivore tabs.
Good luck looking!