You could not pay me enough to deal with this description. Why in the world would you even have or build something like that? Then divert runoff into it, have no filtration and kids throwing whatever they feel like into it.
Even with a salary on top of the $400 budget you are talking money pit ponds and labor intensive with no end in sight because all of the problems are inherent with the design and set up. Way too large, way too shallow, you should not divert sediment runoff into any residential pond. I am suprised there is not a huge mosquito and algae problem also. If someone contacted me on this I would tell them to fill them in and make a rock garden, plant area and kid's playground out of them.
