okay, I am upgrading from my 12 gallon nano cube, which you will probably find for sale here or on craigslist or something for around 100 bucks in a few months, tops. I will probably upgrade to the 28 gallon CF quad. I was wondering if it is possible to add a sump to it, since I would like the great filtration and extra gallonage. I was thinking it would be easier than on other models, because the filtration in the back is uncovered. thanks in advance for any response! 