how about a DSB?, or plenum?
without a source of denitrification, your tank will become a nitrate factory very soon.
I'll tell you a secret I learned from one of my LFS owners the other day. Filters, Protein Skimmers, and all the other devices are just money makers that are totally unneccessary!! They just give hobbyists something to do
sounds like your pet shop manager is too stubborn to take to new aquarium technology..the only reason your LFS's tanks are surviving is because he most likely does water changes everyday. if he didnt, theres NO way a small box filter would help with the bioload of a bunch of fish, inverts, corals, etc.
and do you know what a protein skimmer does?, and i guess you arent running one?