Can't tell. They were tiny and moving very fast. I suppose though they are the hatchlings from the fish that are residing in the park's lake and end up being sucked up somehow in the filtering ponds. Just an assumption.
Could be anything living in a radius for many miles on other ponds, lakes and rivers etc.
It is the other animals, mainly birds that do act as an airmail delivery service for fish eggs around over vast distances. For example, wading birds walking through aquatic vegetation and swimming birds flapping their feet underwater through it. Then the fish eggs in the plants that are sticky attach to the birds' legs and feet. Then they fly away and land again miles away in another water releasing some of the eggs.
Hence you can find quite a number of the same freshwater fish sp. in Thailand that also are found in Malaysia your neighbouring islands.
It works the same with Microfauna, such as Daphnia (eggs) travel along attached to the body of other insects that land in or on waters and fly around from pond to pond.