I made a bunch of these rat cages out of 10 gallon aquariums. I removed the top plastic rim, then with a glass cutter scored the sides in half. Tap from the inside and remove the upper half. Re-glue the plastic rim on the lower half. Now you have a half high 10 gallon aquarium. Or would that be a 5 gallon short? I cut the sides in half so I would have some spare pieces to fix broken sides. Not all will cut easily 
I made tops from 2" strips of plywood sized 1 3/4" wider than cage and 1/4" deeper. Also 3/4 x 3/4 cleats for the underneath at the sides and some strips 1 1/2" x width of top for the remaining two sides. Add some formed 1/2" wire and voila.
I took a couple of pics:
I used these cages for many years until I upgraded to a rack system. IMO the rack system is WAY better but for smaller volumes these cages did great for me. Notice there are spaces for three water bottles and they are "armor plated" so the rats can't chew the bottles. Three bottles definately extends the time between bottle fills.
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Thanks,
Dave Colling

www.rainbows-r-us-reptiles.com
0.1 Wife (WC)
0.2 kids (CBB, a big part of our selective breeding program)
LOL, to many snakes to list, last count:
19.29 BRB
14.19 BCI
And those are only the breeders 
lots.lots.lots feeder mice and rats 

