i have a little bit of sand in my aquarium, but i need to add more. i have half a centimeter of sand. (i know its not much) and i made the mistake of buying hermit crabs and sand today, and i forgot to add the sand before the hermit crabs. i do not know if they will be fine if i just put in the sand. it is my only invertebrate. i need a response asap please. i am just a 14 year old new to aquariums.