Hey Bruce,
What color is the cheato?
Chad
Are you adding iron suppliment? Cheato need it to grow
I'd agree that water changes should be enough. I'd be afraid that adding an iron supplement will cause other algae to grow. Where do you have the chaeto? Does it get enough current and light? Do you turn it over every few days, and pull some if it gets too thick?
I lost a bunch of Chaeto once, I figured out that it was because I was dosing Ca and Alk too close to it. I was able to save a small piece, but the rest did just what you said... Shrivled up and turned brown/clear. I now have the chaeto upstream of where I add supplements.