Beer crates? (sorry, couldn't resist it)
If you are going for the door thing, make sure they are solid timber, not the cardboard stuffed thin walled internal doors, which I do not think would take the weight.
Do you want them all at one height, or stacked? You could look at the steel shelving that you can build up yourself with a screwdriver and adjustable spanner (and a lot of patience). We can lend you the tools if you get stuck. But you will have to check the weight these things will hold, and you may have to put something under the feet to make sure they don't damage the carpet.
Oh dear, I think I may have given you some bad ideas on maximising how many tanks you can get into a room!