Pvc

You dont need a primer, but will give a slightly stronger joint, and clean the pipe of debris before you apply the cement.

Every PVC cement Ive seen says its for potable (safe for drinking) water. Any of them that are for potable water are fine for fish.
 
Use the PVC cement outdoors, and keep it away from any source of ignition. It's quite flammable. I would leave it outdoors for quite a while, as it's stinky, and a pilot light on a stove, or furnace could make it a bit dangerous. Otherwise, the glue is easy to use, just hold the parts together for a bit, as they will try to separate until the glue sets.
 
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