I built my own. The stand designs/plans online were all faulty IMO. Here are some photos for you.
I notched the 4x4's on top to fit the 2x4's and then notched the 4x4's again lower down to fit more 2x4. I think the pictures capture most of the details.
My stand fits my 120 gallon tank 60x18x26. Very strong and will not "rack". You can sheet the outside using 1/4" ply and then add doors, paint or cover with barn wood, or do whatever you like.
I did NOT notch the 4x4's on the ends. I just used glue and deck screws to attach the end 2x4's. I also used small "L" brackets under these end 2x4's.
Oh.... and also I used 3/4" plywood on the top of the stand. The tank sits on the 3/4" plywood. This distributes the weight amongst all supporting wood.
Also not shown, I have (3) 2x4 center braces installed. Each end of these sits in joist hangers. This bracing is extremely secure and strong. The 2x4 braces go across the top to give the tank more support, and also creates an even stronger stand.
Let me know if you have any questions.
Oh and I was able to purchase a radial arm saw, AND a table saw for $60 each from a garage sale, with part of the money I saved. These both cut as if brand new. The materials ran approx. $130.00.