My thoughts on cattails are somewhat different...and necessitated by a desire to avoid chemicals.
If you remove the soil they prefer, you will never have cattails. They prefer loose rich humus soil. If you remove, and granted that is not always possible nor easy, soil to the clay you will never be plagued with them again...at least until your muck builds back up after several years.
Pondrookie, if you can get a back-hoe in there while the water levels are down and remove that humus to the clay, you will solve your cattail problem....at least it works for me and no chemicals.
