I purchased 3 of the fluval 4 internals less than a year ago. The impellor shaft (irreplaceable) is worn causing the impellor to stick. I suspect sand substrate is the cause. I was hoping they would provide some additional mechanical filtration but didnt live up to my hopes. I am considering these, similar to the fluval but with built in UV and price is excellent. Looks to be the same as the JBJ submariner which is over $100. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160417170190&ssPageName=STRK:MEWAX:IT
Good luck , just thought I would share...since I am looking at some similar products