I agree with HN1 and the others.
Also, this may not be what you want, but it is just an idea. You can raise daphnia or brine shrimp. In my opinion, they are really cute and fun to watch. I actually like keeping a bowl of them around, cuz I can watch them and then feed them to my fish once the population gets big.
I get that daphnia are not everybody's thing though. You can do a few shrimp as long as they are small ones. Personally, I would not have an issue putting a few red cherry shrimp in there. I am also a fan of ramshorn snails. They are cute, and snail around a lot.
As for a filter, yes, some sort of filter is preferred. You can rig up a small sponge filter. A heater is only necessary depending on the room temp, and the species you are wanting to keep.