Without knowing where you are from its near impossible to identify a plant from an image, if its one you collected locally. Even if we did know its hard to say, there are so many plants that grow wild that look the same until you get down and look at them under a scope.
A worry with collecting plants from the wild is you can bring in any number of hitchhikers. Some may end up food for the fish, but others could be harmful. It is generally not the most advisable option. Additionally, if you're not from a very warm climate there's a good chance it will die off.