Anyone know how large a Wels would get in captivity? Or is there anyone that has a large specimen? Its a fish I've always wanted to keep and I am working on a plan to to do this. I've looked into it and the average Wels grows between 4-5ft. So far I am thinking my blue print would be 8'x6'x3.5 or 3'. This would be pond measurements and possibly indoor above ground with a glass viewing window.