New Baby musk turtle..i think he might be sick..Please help?

[josie o]

Ok. I've always wanted a turtle. I did my research. I finally got my baby musk turtle in yesterday. I have a 20 gallon tank...filter...heater...thermomteter...basking dock...basking light. Everything I need. The turtle arrived and it is way smaller than I expected. It is not even an inch long. He hasnt been very active from the moment her arrived. I put him in the tank which has about 3inches of water in it and river rocks on one side to provide a shallow area. He laid there and sank to the bottom would move unless i made him. So i figured the water is too deep. I Put him in a small clear container with just enough water to cover his shell. It's directly under the lamp....has a thermometer showing mid 80s. I leave him alone and come back and notice he's moved. but he wont eat the pellets or mealworms that I throw in there. I pick him up and he's almost lifeless. His neck hangs out of his shell and he doesnt pull his head in until i touch him. I have a cave for him to go into but he just hides his head under the side of it. Any advice from someone who knows about turtles would be great. I don't know If he's sick or just stressed. I dont want him to die.