If you can get your hands on any ladybugs, I know its cold now but they prefer aphids as dinner. I would also think flooding the tank for a few hours and scooping out all the floaters would work to. They are not aquatic so the ones that hang on to the plants should drown. A few hours submersed shouldnt effect the plants I would think. A couple rounds and you should be set.
I'm having the same issue with my emersed bucephalandra and other various aroid tank, I have jewel orchids in there as well but I'm going to pull them and drown the buggers (no pun intended) I think I'm goin to leave it submersed a few week to see if I can induce some flowered when I lower it.
Re: Aphids!!!!!!! 
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