Thanks for the reply.

The manual has: "Install the optional fan only if you are using a passive cooler or a water cooler. Installing the optional fan with an active CPU cooler will interfere with the airflow and destabilize the system".

Due to me not having a passive water cooler, and having an active water cooler, I didn't want to destabilize the system.

I think this could have been worded better?

I will install the fan now!!