In plankton swimming around

~3mm long

Edit: He's been in my aquarium and He's growing! now ~5mm long. (26/05/22)

Edit 2: Saw him molt!

Edit 3: ~1cm long (5/06/22)

Edit 4: Molted (12/06/22) ~1.3cm

Edit 5: Molted (16/07/22) ~2cm

It died :( (18/08/22) ~2.5cm

Behaviours:
It can see my hand with the food before it enters the water and will react by reaching out for it.
It can rapidly swim and will catch food particles while swimming.