Anemone in biocube?

For sure. It shouldn't be a problem.

I agree with both of the above. Biocubes are great anemone tanks (I have one myself). Just make sure you have adequate lighting to support the anemone you want to keep.

ac = activated carbon

Just a couple days ago, I responded to a similar question in this thread http://utahreefs.com/forum/forum_posts.asp?TID=53228
Here is a copy of the pertinent part of that post:
The Problem
It's called Alelopathy; the chemical warfare that coral engage in to keep other coral from moving in to their territory. Unfortunately, in our small tanks they are all in the same small territory. The chemical laden water just goes around and around and never leaves. Water changes don't help much. A 10% water change reduces the amount of killing chemicals by only 10%. Larger water changes are a pain, create other problems, and are uneconomical.

The Solution
All reef tanks should run AC(activated carbon) for 2 weeks per month. AC removes a whole lotta chemicals from the water that skimming and algae growth cannot remove. Used to be, before we found out that we should run AC periodically, that there were soft coral tanks and stony coral tanks but mixed tanks didn't do so well. The regular periodic use of AC has changed that.
Just a bridal veil material bag of a handful or two of AC (per ~50 gal tank capacity) in a high flow area, ideally set over or next to a screened pump intake is all it takes.  Pelletized AC is just as useful as granulated because of it's porosity. It also stays easier inside 50 cents worth of bridal veil material gathered loosely and wrapped together with an elastic at the top. Too tightly packed does not allow water to flow past all the pellets.

Hope this helps.

So I have a follow up question to your post Mark - if we don't have a sump going... can we place the AC in a canister filter and run it for a few weeks and achieve the same result?  If so - how much would you recommend to place in the canister filter?  Just the top screen or all throughout?

So in theory could we use the typical HOB filters (like the ones you typically use in freshwater) for this need then?  Just put the AC in the netting and in the bottom of the filter?

Thanks Mark - I'll do that tonight then. :)