Ive had near success with peppermints shrimp, had 6 in my 50 cleared it all but a couple, then they started movin in on my anenonme's then I removed em. This copperband butterfly I got a couple weeks ago cleared my whole tank within 4 days(talk about plague perportions too) The fish does in one day what it takes the peppermints to do in a week though, due to being able to cover more ground without worry of predation.
In the meantime I have a needled syrenge that you can inject em with a kalk slurry if youd like to use.
-Justin