I got the seeds from the hundreds of dandylions at the park. I have to admit, the first few times I tried nothing germinated. That was both pathetic and depressing lol! About a week after the third try some sprouted up tho

I'm still wondering why the others didn't sprout. I don't think they could have been infertile because I think dandylions can reproduce by themselves if needed.
Anyways, if you are going to feed fish dandylions, its best to grow them yourself. You can buy them from a health store, but why buy when you can grow them easily yourself? Its best not to just pick them from public places. They may have been sprayed with insecticides, bug spray, fertilizers, weed killer, and God knows what other harmful chemicals.
I know you can feed the leaves, but I'm not sure about the rest of the plant. The whole thing IS edible, but I don't know if its true for goldfish. A member told me she used to feed the flowers and buds to her mice. I have mice and that is what I will do. People use dandylions as kinda of a tonic. It helps with virtually everything in your body! You can make coffee and tea from the roots, salad from the greens (but I've heard its bitter) and jam and wine from the flowers! How good is it I don't know, I haven't tried any yet
Just a little info that I found about dandylions a little while ago. They are very interesting plants