He hated it so much he said it twice..lol
Ive not tried it myself. Would have thought it would be a bit too fiberous for them, though it is realy healthy and high in vitamin C. Stick to cucumber shelled peas Courgette and carrot.
...and potato, and sweet potato (my bns favourite and very good for them), beans, broccoli stalks...there's all sorts of veg you can feed.
I personally dont feed cucumber and probably wouldn't feed celery, they have a high water content so the fish wont be getting as much nutrients out of them as they would the same amount of (eg) courgette or sweet potato