Spacing for rack tubs?

I was wondering if anyone uses cardboard box for tub spacing while building a rack? I have used CDs and the wood swelled and makes it hard to open their tubs. Just need some ideas on what would leave a good gap, but not enough for snakes to get out!

I've only used CDs.
I wouldn't have the opening larger than 1/8 of an inch.

Are you building a new rack? Have you thought about building it out of PVC plastic?
They don't swell like wood. They are water resistant and lighter than melamine.

add a few more cds

No, there is no place near me with xpvc.

When i made my melamine rack i spaced it with 2 cds and it was perfect.:gj:

I couldn't find a place near me with xpvc either but i contacted my local lumber company and they got me an equivalent this stuff called azek pvc sheets. The rack works out perfect :gj: so much lighter than melamine but more expensive.

CD's here as well. I'd love me some pvc racks, but Chad complains about the price of melamine, so I could just imagine what he would say about buying pvc :rolleyes: