I don't know whether its possible or not to go pellet free.. But I imagine if you have the proper balance and variety it could be an option.. I would be curious it if can be done.. Cause I am all for treating my pet as closely to natural as possible..
Here is a List from here of things you can feed your turtle.
viewtopic.php?f=8&t=5I would imagine you need to add more vegetables to his diet and also make sure he is getting lots of calcium, in the form of live prey, cuttle bone or calcium power sprinkled on his food..
Hope the list helps..
I also forgot to ask what kind of turtle is it.. Depending on the species I am sure it has different dietary requirements..
Midland Painted--Philbert--SIP
1-2 1/4" Mississippi Map Turtle(Male)--Atlas
1-2 1/2" Western Painted Turtle (male)--Titan
40 gallon tank