I've just started cycling a 29 gallon biocube which I want to eventually use for an octopus. I have about 1 1/2 inches of live sand, about 30 pounds of live rock in the tank, and about another 8 pounds live rock rubble in the filter (I used the live rock rubble to replace the bioballs the cube came with). I also added an extra bag of activated carbon. Two questions so far. First, the filter area in the back of the tank is very accessible from the tank -- there's about one inch of open space. Any ideas on how I can close off that avenue of escape? Second, I don't see where there is room to add a protein skimmer. Any thoughts on whether one is necessary and, if it is, any thoughts on where I can add one to an Oceanic Bio Cube 29? Thanks for any help you can offer.