I'm glad you found some solutions to your woes! You said a ribbed 'cone'? A barbed fitting maybe? Cones tend to get pretty small. For me, really 2 areas that will make flow noise. - the intank part: here I use media bags in the top shelf with some GAC and some PhosGuard in them, and it keeps the flow sound real quiet. - the hose going into the sump, especially since it does have some air bubbles in it also: If this is a problem area- Google 'reverse durso'- that will take care of that area. Good luck my friend- of whom I am so envious of b/c you live in Japan! Keep us posted.