For a nice change, I thought I'd post a DIY, that doesn't include Flower Pots (hem hem).
Like most people, I guess you get sick of all the crap that just gets tossed into your under-aquarium cabinet/shelf. And when you're constantly digging for items you use regularly, it's a pain. Here you can see the Food Storage Rack I threw together, much in the style of a Kitchen Spice Rack.
First up. I took note of the cannister size of fish foods I use regularly. And decided on how many cannisters I wanted across each shelf. This gives you your base width, and base depth. Make sure your shelves aren't so wide, you cannot close the Cabinet door.
Now very importantly, think carefully about the height between each shelf. You MUST be able to clear the shelf above, when you place, or remove, a cannister. So you need to leave some manoeuvring clearance, both upward, and forward. (Reducing the height of the shelf front would aid this). And again, watch the height (with cannister) of the top shelf, or your door won't close.
What I began with, was a back panel of 3mm MDF (Medium Density Fibreboard). On to this I glued (PVA Woodglue) and tacked 9mm MDF for the base, and sides, of each shelf. I then pre-drilled, and tacked clear Perspex, to the front of each shelf. The whole Rack is then screwed to the Cabinet door, through the back panel. I used four screws, but I'm sure two would suffice.
So there you have it. MDF, Perspex, PVA Glue, Brads (little nails), Hammer, Drill, and Jigsaw (power tool), and about an hours effort. If it's not obvious why I used clear perspex, note that I have a good view of exactly what is on my shelves.