I heard that they can inhale gravel but apparently not sand, can someone please direct me on this? I also heard that Plecos LOOOOVE playing in sand, but I just want to be sure that sand won't hurt my little baby I also heard that gravel can hurt the mouths of Plecos, so obviously I'm leaning towards sand, but I don't want him to inhale it or anything. Obviously I can research this myself, but there's so much controversy on the subject and I don't know who to believe. I think I might be turning towards marbles, but I barely know anything about that either, plus I have Guppies in the tank as tankmates for the Pleco (adults, not fry, even though Plecos probably won't bother fry but just to be sure) and I don't know if marbles are okay for Guppies. I know a great deal about gravel and a great deal about Plecos, but nothing about when the two come together, and other substrates such as sand and marbles are a foreign world for me, plus we're adding guppies into the mix which makes it even more complicated, so I'm pretty much clueless here, any info would be greatly appreciated.