I saw some water wisteria at petsmart the other day, so I got it to see how my goldfish would treat it. I figured it would get shredded given that it looked similar to lettuce in texture and the leaves were not overly strong. I was right! All that is left is the stems! I'm going to put them in a bowl and see if they regrow.. if they do, the goldfish get two treats for the price of one!
Jim