I really hope this is your quarantine tank. The bio wheel should come off, but let it float in the tank for about a week then take it out, so not to put the tank into shock.
But the big thing is keeping a naso tang in a 25 gallon tank??? Thats disaster waiting to happen. Not to mention the size he'll be getting soon, but with the other fish, your tank is in need of upgrading to keep the tang.