Sniperhank said:Well that is open for debate. The bigger the better when it comes to sumps and it also depends on what all you want to put in it. On my 55 gal I am running a 20 gal long as a sump. I have a fuge w/ cheato, mangroves, a money plant, and the heater in the middle. My intake section has my skimmer and uv sterilizer (which is worthless and will be going away soon). This still leaves me lots of room for anything that I could want.