You can run it however you want. Passively in a media bag in the sump, a media reactor, a canister filter, or a HOB. It is more effective in some applications, but it should work well enough in the AC20.

I've been running it for about 2 months now. It will cut down on your algae but it does take awhile to strip the system of all phosphates. Reminds me I need to change mine as I can see algae starting to grab a hold again.