In a pond, there are so many different places…
There are niches right at the water’s edge.
There are different ones, just a few feet deeper into the water.
Then there are other niches very deep in the water, and others deep in the soil at the bottom of the pond.
There are niches associated with algae growing underwater and others growing on plants floating in the water.
There could be shady parts of the pond vs sunnier parts, where organisms that prefer one or the other prefer to grow.
If the pond is large enough, it might have an island, effecting creating a barrier from the rest of the shoreline and possibly a very specialized niche…