Yes, alas. The Zilla Critter Cages are made with thinner glass than aquariums, so, they can't withstand the pressure from much water. Hence, tupperware. I only noticed after I bought the thing, brought it home, and then opened it. It has a wonderful little piece of paper saying "DO NOT FILL WITH WATER" inside it, as well as a bit of small print on the front sticker. I McGoogled it, and, well, it just doesn't seem worth the risk. I'm willing to work around it, because I won't find a tank of this size for what I paid for it (half-off sale).

Looking over my options and how much it would cost compared to just biting the bullet and buying the pre-mix, I think it might be cheaper to just return the Eco Earth and buy a couple bags of the ABG. Of course, that brings me back to one of my original problems: can I set the bottom of my water dish on the floor of the tank and build the false bottom around it? Otherwise I'll have to buy, like, six bags of ABG, which, no.