GFO and cheato ????
 

IF you run a GFO is it likely that your cheato won't grow?

I run GFO and my Cheato grows very well

That's hard to predict. The GFO is consuming phosphate, but phosphate might not be the limiting nutrient in your system.

im just having trouble growing chateo-but the culerpa grew like mad almost to good

The Caulerpa likely is outcompeting the Chaetomorpha. That's quite common.