The way I would do this is to wet some paper towels with the tank water that you have it in.. And take him or her out of the tank and try to see what it is mabey it is a gravel or something.. If it is they can most of the time spit them out after a day or so when they get hungry.. I hope that helped out some.. I really dont know what else to tell you...
What size gravel do you have? if its too large to fit in its mouth, then it could be a bad case of mouth rot. If it is then you can clear it up quick with this product. Fungus Tabs
I tried finding a picture of it with no luck....sorry
Take the guppy out and put it on some wet paper towels, then try and see if you can get it with some tweezers. If you're willing to try and poke it with a needle if you think it's food or something, but if you think it's mouth rot I wouldn't send a picture of it if at all possible
