Board Thread:Dragon City Questions and Answers/@comment-99.249.175.235-20130515225600/@comment-24658159-20130822014542

Yeah, Rawrshaq is correct. The easiest way to breed Plankton Dragon is by breeding a Lvl. 10 (or above) Sea Dragon and a Lvl. 10 (or above) Terra Dragon. The first result will be Mud Dragon and second will be Plankton Dragon. Try it. It worked for me :)