elodea or pond weed and probably arrow root are the hardiest and moast recommended for beginners aquariasts

Don't know where I thought I read my anacharis plants were a possible good plant for my g-fish tank, they do get nibbled on a bit, but the majority seem to be fine after strapping them lightly to little stones with a rubber band. I finally did this after 3 weeks of re-planting the floating pieces ever day      they like to eat at the roots

Feed them lots of veggies! It's great for the digestive system of your fish (: And they contain fiber and important vitamins!
I use to give my fish green peas (: They are very easy to prepare, just buy frozen, natural peas, thaw them and pop them out of their shells and you're ready to go! Unless you have small goldfish, then you might need to cut them to some smaller pieces (:
Other things you could try would be big chunks of cucumber, zucchini, lettuce and orange (:
The lettuce could be "planted" in the grovel for your fish to graze on, or attached with a clip to the side of the aquarium. And remove any leftovers after 24 hours. Be careful with the orange too, take away all the peel so it won't get stuck in the mouth of your fish. Oranges contain lots of acids and juices, so be careful not to give too much of it, as it may pollute your water (:

Other than this, have fun with your fishies!

Do so! They've got really big and thick leaves, so your goldfish ought to leave them alone d: