When it comes to materials you can pretty much use anything that your woodworking skills and tools allow ya. I used the Birch plywood because it was the easiest to work with without making it a major furniture type project.
But if you have a pine stand you can build the canopy out of pine and stain it to match....
This is how the Birch Plywood looks after i stained and varnished it.
If you would like to stick with pine that would be also very easy to do since sizes of up to 1 x 12" boards are usually stocked at any lumber store. Just sit down and think of how "tall" you want your canopy to be and buy the pine boards accordingly.
For example...If I was to do my canopy pictured above with boards I would have bought 1 x 12" Pine to use since this canopy stands about 11" high.
If you wanted a lower canopy just go to 1 x 10, 1 x 8 etc. (its all up to you)
After it was built and stained I used Spar Varnish to seal the wood... it is an int/exterior clear varnish that will protect stain and wood from moisture...
DIY Canopies are actually very easy and very "cheap" to build. That one in the photo cost me about $45 to build ( - lighting of course)
That amount includes the wood , screws , hinges , stain , varnish...the works !
If you need help just email me the exact dimensions of your tank and I will see what I can come up with.