Well, if you are trying to recycle some wood you already have, I suggest this very simplistic furniture plan as reference, because of low needs of material:
Ana White | Build a Benchright Farmhouse Bench | Free and Easy DIY Project and Furniture Plans
I had a broken slatted bed base like this:
And became this:
I had to buy three more pieces of wood, but it ended up costing me less than 15 dollars (including the nice box below). It took me quite some time because I worked with very simple tools, like Swiss knife and plastic ruler... but you can make it in one day with proper tools.
Btw, mine is a 14g tank.
If you are going to buy the material, maybe it would be interesting to check other plans in the same website I sent you.