I have a dwarf onion planted in a dirted tank with a plant light - it grows really well. However, once a leaf reaches the top of the water the leaf curls and the breaks off.....any ideas why? There is no top on this tank, and I don't fertilize it but I do have a bubbler for surface agitation. My lighting is a 25 watt florescent growlight for plants that I just lay over the top of the tank (I am cheap and refuse to spend gobs for an aquarium specific one) All other plants are growing great - I have to trim back about once every 2 weeks or stuff starts trying to invade my bedroom. I have other low tech plants like wisteria, java fern, java moss, X-mas moss, moneywort, crystalwort, hornwort, and anubias nana - all doing great and have been divided more than a few times - I have stocked most of my other tanks from this one....just not sure why the heck this one plant is acting weird. Any clues?