I want to add a 20 gallon sump/ref to my 29 gal but dont want to drill my glass can I use a back filter and tap the bottom of the filter and add a valve to regulate flow and gravity feed to the sump then use a return pump with a spray bar for return? If there is no major reason why I...

Man, some people can think up anything. Check these out Though I still think my veggie clip on fishing line is just as good and doesn't require half the work http://mistressreef.homestead.com/files/diy/diy.html