
After having bought a Petco brand 12-oz bottle for my gerbils that leaked like crazy, I bought on a 12-oz Super Pet glass water bottle. Unlike the Petco 12-oz bottle, this one was much too tall to fit into my gerbils' 10-gallon tank: the body of the bottle was too long and the spout was at a much more vertical angle than the spout of the Petco bottle. My fault. Otherwise the bottle worked well.
I then bought a 6-oz Super Pet bottle. It was a good size relative to the tank. I liked using glass rather than plastic, esp. since there are no BPA-free plastic bottles on the market. (And even those tend to taste plastic-y.) One problem: after the first dribble of water on the first day I bought it, no water came out! I didn't realize for a day, and when I checked -- which I sometimes forget to do! -- it was completely dry. No amount of tapping could make the water come out. I held the larger bottle in the tank for the gerbils to drink from, and they clung to it, drinking continuously for a couple of minutes. They were completely parched! They could have died. I felt terrible.
As previous reviewers have noted, these bottles can't be hung in glass tanks without a water bottle holder, e.g. this Bottle Guard Water Bottle Holder 8oz. These are worthwhile to have anyway, in case you have to switch to plastic bottles: they also prevent little animals from chewing on the corners of the bottle. However, because of the angle of the spout on these Super Pet bottles, the bottle tends to sit a little awkwardly inside holder, higher up than it should. So it goes.
TAKE-HOME MESSAGE: If you buy one of these bottles, hoping to protect your animals from BPA or to avoid chewed plastic, CHECK *AT LEAST EVERY DAY* TO MAKE SURE THAT THE WATER IS COMING OUT. Otherwise your animals might die of dehydration. And then you will go to pet-owner hell.
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Super Pet Small Animal 6-Ounce Chew-Proof Water Bottle.