I have the XP3.
No problem at all. No water will gush out. Just leave the two tubes (hoses) in the tank where they are.
1. Unplug it
2. Wait 2 minutes
3. Lift the lever on the top (you'll hear a suction sound)
4. Once the lever is separated from the canister change your media in the canister. DO NOT PUT ANY WATER IN THE CANISTER AFTER YOU'VE CHANGED YOUR MEDIA.
5. Place lever back into canister snugly and close the lever (push it down totally)
6. WAIT 10 minutes. As you wait you'll see water from the tank filling up the canister.
There is no need to prep anything because there is still water in the tubes (hoses). The only time you will have to prep it again is when the tubes (hoses) have been taken out of the water completely and the water in them has been drained out.
After you've waited 10 minutes plug it back. You'll see some air bubbles coming out of your supply tube.
You're good to go.
If you hear a prolonged "rickety-rack" sound coming from the canister simply "re-boot" the canister by unplugging and re-plugging.
Good luck....it's quite easy
