Your pictures are not adequate to see enough necessary details of the plant to give a good identification. Guesses yes, specific name no. Read through this thread and see examples from the archives on how to get good pictures for use to provide a better name of you problem plant.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=371748#Post371748

An important thing to see if it is Sago pondweed is to see closely the arrangement of and type of the leaves at the top end or the top stem or plant.

Last edited by Bill Cody; 07/16/15 08:55 PM. Reason: spelling correct

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