This is a good read and lots of good advice for sure, but I do have some thoughts I'd like to share. I am a pretty avid woodworker, I have build A LOT of tank stands over the years from fairly nice stuff to these basic 2x4 type stands, and I am very familiar with The King of DIY Joey's stuff. I have recommended his designs to others on this forum who are looking to build a solid, functional stand without a lot of woodworking experience and/or tools.
I love Joey, but also look for plans by
@RocketEngineer who fortunately for us is an R2R member. Maybe if he's not busy he could stop by and offer you some help here too.
To clarify something, in woodworking "S4S" means "Surfaced on 4 Sides", which means the wood has been machined down from it's original dimensions from when it was rough cut at the sawmill. For example, a 2x4 measures a true 2" x 4" when it leaves the sawmill as a rough cut 2x4. It is then machined down (on all 4 sides) to the 1.5" x 3.5" that you see at the store. This final machining also straightens the board and removes all of the rough saw marks from the sawmill.
S4S is NOT a statement or description of the board's quality. The crapiest boards ever could be S4S.
Here's a woodworking guy I like very much, Marc Spagnolo, aka The Wood Whisperer, with his explanation of S4S:
https://thewoodwhisperer.com/articles/s2s-and-s4s-what-gives/
At Home Depot, you can use just about any of their 2x4's to build a perfectly strong and stable stand, just pick the straightest boards you can find, as others have said. Ideally, look for their premium, kiln dried (labeled as KD) 2x4's. Should be somewhere around 4 bucks or so for an 8 foot board, depending on your exact market and your store's inventory. I think my local sore has them for $3.70 or so.
I would not suggest using pressure treated wood anywhere in your build. Although newer stuff is arguably safer than in the past, this material may have chemicals that could be harmful to your tank or you and your family, and it's just not needed. Your finish - you mentioned paint, but could also be varnish, oil , etc., will protect the stand from the occasional spills.
Likewise, I would not suggest using marine grade plywood. In a perfect world, sure, but it's not available at Home Depot or any home center that I know of, and it's very, very expensive. In my opinion, this would be entirely overkill for your stand build. Save the marine grade stuff for the boat builders ;-)
While you *could* use 3/4" plywood on your top and for wrapping your stand, that would be entirely overkill. I know Joey sometimes uses 3/4 ply, but that's on his very large tanks (like 200+ gallons). Your 60 gallon doesn't need 3/4" skin, which will be more expansive to buy and harder to work with than thinner stuff. The plywood top and sides are just to prevent any twisting or racking forces from forcing the stand out of shape. At the most, I would use a piece of 1/2" ply on the top, and 1/8"-1/4" to wrap the sides. If you're building your stand like Joey advises (and he has more than one design), the 2x4's will fully support the weight of the tank. The top is to resist racking and the side skins are largely just for looks. Plenty of people run these 2x4 stands without the sides, and some even with the plywood top.
Generally, you don't want the rails (horizontal supports) to span more than 36" without a middle support, so most would recommend a middle support for your 49" long stand.
I hope these suggestions help! Please post again with any further questions, I enjoy talking about stand building with others, and I'm always glad to try to help with DIY stand builds.
Good luck with your stand!
