Another suggestion is to check out yard/garage sales, craigslist etc. for old aquariums. If you can't find tanks with lids you can always put plastic wrap or a board over the top to keep the cats out. I plant them as terrariums but I've heard others talk about using them as a holding tank (so to speak) for a few plants that like extra humidity during the winter. If you go that route, just be sure to wash them really well (especially if they were marine (salt water) systems.
