My design has the aquarium overflowing into the bio filter. So I had to lift the aquarium to put the top of the aquarium near to the height of the the 35 gallon drum being used for the bio filter. First mistake was trying to drill hole in a 55 gal aquarium I found out that even that big of an aquarium may use tempered glass. Mine did so I have an acrylic one ordered . I picked a pre cut piece of plywood to put the aquarium on. I then bought a 6X6 and cut it the length of the plywood boards width. I only had a circular saw that I had to cut from the top and bottom so it is not perfect. I cut six pieces and stacked two on top of each other to make it 12 inches tall. But a 6X6 is not 6 inches it so it is shorter than 12 inches tall but the plywood also adds height. It worked for my 55 gal. aquarium. I am waiting on my new one to get delivered. The first pic shows the set up.
I then put my black pipe frame that will hold the plants on top. Wood had small gaps to I added weights to hold everything firmly as I screwed the frame down to the wood. The screws go through the plywood and into the first 6X6 to make everything firm. If I make another one I will not use black pipe instead I will use square tubing and just weld it all. I will make a video to show how to make a black pipe square because when you screw in the last threads it unscrews to other end of the pipe. But back to this assembly.
I then used a board and screwed it onto the front and put a screw into the front of each 6X6 end. I stained and sealed the wood first. I will add another clear coat after I get it all finished but before adding the aquarium.
I ran into a problem on the back because I am not a carpenter the ends do not line up. So I will buy metal plates so I can screw the two 6X6's together. The screws coming down through the plywood are more than enough to hold. Not that it will move when full of water but it is at a school so it may need to be moved some day.
I will add more steps ...