Size for overflow.

I don't think I've ever seen a canister filter used with an overflow. What exactly are you trying to do?

Should have an intake tube and an output tube. You cannot run a canister on an overflow unless you spend every moment of every day adjusting as the flow changes

Canisters should come with some hard plastic intake and output tubing. Usually with a barbed end to attach a rubber hose to. Most small to medium sized canister filters use between a 1/2 inch and 3/4 inch inner diameter tubing.





And just to make sure you are not getting things confused. This is an overflow.
View attachment 983073

On you tube, a guy named Joey had tutorials on how to build, They are quite and reliable, in fact I am in the process of changing all my expensive ones to these!

He also has a forum diyfishkeeper which has step by step instructions on the stuff he built in his youtube videos. He has some good cheap ideas that will definitely save quite a few bucks

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If you're looking for the tubes that Zuki posted, that's easy to acquire.

First, figure out EXACTLY what type and model of canister you have. Then, tell us. We can work with you to help you figure out what you need. Pics would be helpful.

Once we figure it out, we can direct you elsewhere to buy them. I buy all sorts of miscellaneous odds and ends from Amazon for my filters. Stuff like tubing and intakes. I'm sure we can find the factory part that does exactly what you need it to.