Eheim for sure. I just picked up a Classic 250 that sits just feet from the head of my bed and I can't tell it's there. For a 40g I would say get the 2215 at least, if not the 2217. If you need the extra gph flow rate. You can place whatever you want in the media trays. Drawstring filter bags are handy if you want to be able to remove media. I just run what it comes with as it's rather good. The carbon pad can be left out all together and saved for later should you need to remove medication or something similar.