Looks like it might be Sepia bandensis - good news if it is as they get to a maximum of 3-4". I had one for 8-9 months before - it was not a juvenile when I bought it, and yours is a baby so you can expect a longer term with it. Just wait until it gets a little bigger so you can better see it change shape and colour it is amazing to see. There's not a ton of info on keeping these guys (try TONMO), but advice I would give you is to not feed any fresh water fish such as guppies or goldfish when it is bigger. You can train it to take food from a feeding stick after a while. There have been some anecdotal reports of cuttles dieing after being fed guppies and mine did after I had done so - might have been the cause of its demise or it could have been approaching the end of its (short) natural life. They like tanks that are tall and will stay on the rocks, bury themselves in the sand, or hang on the underside of a chaeto (or another macro algae) raft floating at the tank surface.
