What is going on/ is this?

[archangelvk]

So I set up my NEW 33 gallon long tank around 2 weeks ago. A week ago I took 4 Amano Shrimp from my mature tank and put it in the 33 gallon to test the water and make sure the cycle was good enough for fish. The ONLY plants I added were all purchased for this tank were Tropica 1-2 Grow cups as they are pest and algae free. Today I look in my tank after a water change and to my surprise/horror I see THOUSANDS of these little things that look like super small tadpoles jittering all around the water. I thought Amano shrimp needed brackish water to hatch/survive? Are these even amano shrimp? and if they are and dont survive, will it create a ton of ammonia due to dead livestock? Theres currently ZERO fish in there and Im thinking about putting some in just to eat whatever this is?

 

[SaraB]

Does it look like any of these? Aquarium Microfauna - The Aquarium Setup, Filtration, and Maintenance Site
It might be some copepods by your tadpole like description, harmless and future fish will eat them.