I don't know, nevergone, I was doing some more research online tonight and I was seeing quotes as large as 24", but noone who actually had one over a foot long. They must grow pretty slowly. I wonder how long they would live if given a chance.
A lot of people think clown loaches only get to 6", but that just because they don't care for them right. They should grow to 12" or more and live for decades. I suspect it is the same with weather loaches. They die young because they aren't given the ideal enviornment. I bet a small group would do well in a 75 gallon coldwater setup with a varied diet (bloodworms, veggies, etc.).