Advice for my DIY. 330G

[Mordarius]

I hope not but i shall see
But back to subject. what thickness of ply would work best for this size tank?

 

[kallmond]

I'd use 1", which is around 25.4mm. I'm not sure what the standard size is for lumber in metric, but whatever the closest to 25mm is what I'd use.

If you're going to do an external frame, you could probably get away with the next size plywood down, around 20mm.