I am a beginner and recently purchased an aquarium for my classroom. I have 2 yellow labs. One big about 4inch and dark in color the other 2inch and light in color. They have only been in the 20gal for 3 days and haven't eaten at all. I even place the food close by them and they still won't eat. They stay towards the back bottom of aquarium and stay in their hidding places all day. Even when the room is totally quite and you don't move they still stay put. My food crisps said to feed them one crisp per inch of fish 3x's daily. I did this the first two days but today the third day I just feed them once and only four flakes because I'm worried about building up to much amonia since they aren't eating. Will somebody please tell me whats wrong and how to fix these problems. I don't even know what gender my fish are can someone help with that too.