Highschool + Pond = Bubble Fountain AT LEAST once a year. Probably more like 2-4 times a year. Wouldn't bother putting anything in there that can die.
This is going to be one of your biggest problems. If you can get it working by any means then that's awesome, but it really doesn't matter if all of your fish get killed by some juvinile [censored][censored][censored][censored][censored][censored][censored]. Believe it or not, the first thing that a "normal" kid (for this decade) thinks of when they see any type of potentially volatile display is "I could screw them over by killing their fish/plants with ______."
Not saying that it isn't possible, but it's sketchy at best. I'm in a similar decision making situation as you are with a club that I'm leading at my college. We're planning on setting up tanks and Aquaponics displays around campus, but there's the issue of the average unsupervised American teenager. The solution has been to lock anything we do down tighter than anything you've ever seen. Even with that solution, we haven't done anything good yet.
Another thing is that it really needs to be designed. If you have a drafting or engineering class at your school, see if some of those students could help your class for extra credit or something. Come up with the design constraints, send them to the designers, then have your class build it exactly as the design shows. I'm talking 3d models of all the plumbing, plans for the thickness of materials, ratings for the planned materials, everything! You absolutely cannot just build this kind of thing, if it was an individual doing it then the story would be different, but some form of solid management and plan has to be in place with this number of people and this amount of funding. Remember, you've only got one shot at this, if it fails this time, you (and probably anyone in your district) will ever be allowed to try it again.