Originally posted by Harlequin
they seem to pulse when I have the powerheads off when I change the water. And no they are not in direct path of heads.
I suspect it has more to do with the water change than it does the powerheads being off. Mine will pulse like crazy right after a water change, then over the course of 4 weeks or so, they slowly stop pulsing. Then the water change, and they're back pulsing again. I'm not sure what it is about fresh water... but it's got to have something to do with some water parameter. I've read it might be alk/ca, but I can't say one way or another.