On Sun, 6 Jun 2004 23:30:52 -0500, "Tom B."
wrote:

I want to replace the plastic ribbed hoses that cam ewith my Fluval 204 with
vynal tubing, but I dont know what size I should get. I am mostly worried
about the connections at the filter, the input output ends will have custom
PVC joints going into the tank.

Stick a tape measure across the connection and see what you get. I
have one running in the other room that I would say it's probably
5/8".

Why do you want to change hoses, though? The ribbed hose (they grey
stuff) doesn't kink and hides the ugly gunk that you would get in
clear tubing.
If you want some, btw, I'd suggest a LFS rather than a hardware store.
You pay 2x as much but it's a lot more resilient. The stuff I've
always seen in the plumbing area is already pre-kinked from storage.
You may find higher quality tubing at a winemaking supply store or
something similar.