If "good flow" means alot... I've found they don't really care for that. But if it was doing fine when it first got in to your tank, and the closing up is a recent thing, then I'd suspect something in the water is ticking it off. Either chemical warfare like joy mentioned, or excessive nitrates/phosphates/etc. If that *is* cyano on the stalks, I'd get that off also... it could be irritating it.