Normally in low flow fuge only one side of the cheato is lite and grows. If you have ball of cheato and enough flow. It will spin and have new growth on all sides.What you mean make the chaeto spin? I put some chaeto in last time and it slowly died our after about a week which makes no sense to cause my phosphates are .85 so it should of fed off that
If your last ball of chaeto died, then I would look at your light and water parm.
I add "Chaeto Grow" from Brightwell and get great growth. Chaeto actually will strip out keep elements from your water as grows. Not just phospate and Nitrate. That your corals need too.