If you're having trouble with veggies try anacharis. It's an aquatic plant, fairly cheap and easy to grow. Every turtle I have had eat the heck out of them. To avoid having to run back to the pet store all the time you can just pick up a cheap $5 Tupperware bin throw them in there in some water and sunlight and grow your own. Watch out for snails though! Guaranteed to be on live plants and although a tasty snack for your turtle not such a tasty snack for filters and their breeding rate can get out of hand.
As for the cichlid pellets I've never seen that before but it seems like a great idea! I'll have to try it out.