I'm going to be looking at a 50gal Seaclear System II from CL tomorrow, the guy wants $45. It's the tank only, without any of the filtration system, Has anybody had experience of these, the manuf website doesn't give a lot of info and only lists the skimmer and pump as available spare parts so I was wondering if I could put anything else in the 'overflow compartment' on the back for filtration/circulation?