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Discussion Starter · #1 ·
I'm helping out an elementary school that has "nature courtyard" that includes a 800-1000 gallon fully contained pond. They keep an eastern painted turtle and a school of feeder goldfish in the summer. There is also normally a spring explosion of tadpoles and then frogs which then make their way out of the pond.

For plants, they can only manage floaters, like water lettuce, hyacinths, and lillies. I give them weekly quantities of the salvinia minima (spangles) that has explosive growth in my 50g tank. There is a normal and healthy amount of green algae that covers the pond sides.

About this time of year however, after all the tadpoles are grown and gone and I think the pond stabilizes, the floaters turn yellow and start dying. We took an API master kit nitrate reading and sure enough it is < 5ppm, so I am pretty certain that is the reason for the floater demise. The question is, which that much water, direct sunlight overhead, and only doing floaters, are we looking at trouble if we put plant nutrients in the pond water column? All of the pond plant nutrients I have found are pellets that need to be embedded in the dirt at the bottom "near the root zone", but they don't have planted plants, just floaters, which I think the plant pellets are not for. So I think I need to use regular ferts like perhaps my NILOCG dry ferts but am worried of creating a giant algae bloom in those conditions. Some threads show that people rotate their pond floaters to a bucket with fertilizers for a few days and then back into the pond for this kind of issue. However they are not going to do that. Is there anything else we can do?

Also, the turtle winters in a "studio apartment" spare tank at my house. They don't shut the pond completely down for winter and leave a bubbler, but plants obviously do not make it to next season, just occasionally goldfish.
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