I forgot you had the baskets out of the Fx5. When you don't have them in the Fx5, the canister can not purge completely. You will never get all the air out.
Replace the baskets w/o media and then check for air. You may want to force purge a couple times by unplugging it.
Replace the baskets w/o media and then check for air. You may want to force purge a couple times by unplugging it.