What adjectives plants do goldfish put away?

I'm doing a jar ecosystem lab in science and we are allowed to put in almost any adjectives plant life but we're not allowed to put in any fish food or anything approaching that. I have a goldfish in my tank and he's lived for roughly two weeks with just pond mud, two sprigs of hornwort and duckweed. Is there anything else i could put contained by my jar to help my goldfish live longer??
Freshwater aggressive fish reservoir?
Answers:    I agree with the previous poster, no honest teacher should be using a jar to torture goldfish. If you must do an ecosystem project, use ghost shrimp, not goldfish.

Goldfish need 15-20 gallons plus, they will not live long surrounded by a jar, it's entirely stressful and cruel.
http://www.theaquariumwiki.com/Goldfish
Marine Coral Help?
You put a Goldfish in a JAR? That is a BAD school project. Each Goldfish should have at tiniest 10 gallons! Pond mud is NOT good for the Goldfish either, what kind of experiment IS this? You should boycott the don... this is cruel.
My fish have ick... ?   My convict babies preserve getting sucked surrounded by the filter... should i turn the filter bad? till they grow?   Should I hold blood parrot and angelfish surrounded by one and the same container? ?   Whats surrounded by my fish container?