Algae need two things to grow - light and nutrients. The more light, the faster the algae grows (providing it has the nutreints it needs). All plants, including algae, will stop growing/die if either light or nutrients fall below their minimum requirements. Temp also has a limited effect here. Again all plants have a temperature range that they like. If you get too far out of that temp range they die. (FWIW I don't think temp is a problem here)
Now to your problem. I don't think 22 w bulb is enough for chaeto. I know mine did nothing with 1 of these bulbs -
http://www.reefcentral.com/forums/showthread.php?s=&threadid=313318 - within 6 inches of the water surface. It depends upon the wattage and how far above the surface the light is. When I added a second bulb, then the chaeto started to grow - not fast but grow. I will be installing a MH light (to use the "old" display bulbs later.
As for nutrients - even thought your test kits say 0 phosphates/nitrates/nitrites, it could be because the caluerpa in your display is using up the nutrients leaving nothing in your water column for the chaeto that you are trying to grow. The fastest growing algae will absorbe the nutrients first.
Iron could also be a limiting factor here. I don't usually recommend dosing something you haven't tested for but iron is the exception. Here is an article explaining iron and macroalgae -
http://www.advancedaquarist.com/issues/aug2002/chem.htm
I would double dose iron, increase my lighting and pull out as much of the algae in the display tank (caluerpa as well as any other - slime, cyano, etc). This increase in lighting and nutrients may give the chaeto a kick start and achieve what you are looking for.
Vickie
