This is for a 28 gallon nano cube as far as water ever hitting it that's highly unlikely,the stand that this setup comes with is that compressed crap plywood that expands the minute water hits it so I think any wood is better than that.the only reason for building the stand in the first place was for 2 reasons (1)the crappy stand it comes with didn't match my furniture in my living room.
(2)it's so unstable due to the poor design.the wood I used was NOT marine grade.basically pine 2x3 and birch plywood..and like I said anything is better than what it came with.my stand now never seen water and I'm sure the one I built wouldn't either...ooh I also glued every piece as well as used 3 inch screws..I was 4 screws shy of using the whole box..as far as stability me and my buddy sat on it at the same time which was well over 400 plus pounds and it was solid...if you need anymore info let me know