I saw on SubetaHQ that the Dream Gem turns your pet into a galactic pet, but I don't know how to use it. T.T Am I correct?

You have to go to the Coda Caves on the 6th or 7th day of the month and start a quest there. You will be asked to turn in a few gems (usually 3-5 I believe), and if you finish that quest your pet will be turned in to the color Galactic =)

The Dream Gem alone doesn't turn your pet into a Galactic pet. On the 6th and 7th of every month you can go to the Coda Caves on Atebus, and there will be a link to 'Bless your pet'. Once you start the quest you'll have to bring back 4 different, random gems to get a a galactic pet.

So this is why everyone always asks how to use Dream Gems :o Does SubetaHQ really say that you can use them to turn your pet Galactic? o.O;

SubetaHQ shows an image of the potion you need for every color at the Pet Viewer. However, because Hydrus and Galactic don't need potions, I guess they just chose an item which was related to the color (Hydrus show a piece of the Uncharted Land Map).