I have read that they can get up to 19". But as we all know, you can't believe everything you read on the internet. I had a couple in a 20 a few years back with plans of moving them to a much bigger aquarium in a short time. Sadly the move to a bigger tank never happened and I gave my weather loaches away. They were some of my all time favourites and I would love to get some again. So what are some of the biggest you have ever seen?