Baby apple snail + Future baby shrimp

I have never actually browsed this section properly and it seems have missed out on a lot of useful info.

I found a small baby apple snail in my aquarium? The mother has never laid eggs or even had the required room/gap between water surface and aquarium lid so I'm really curious as to your thoughts and theories as to how a singular apple snail was hatched. Also I have some Juli cory cats, will the snail be safe or should I move it to another tank?

I also added some tiger and bee shrimp. I found the tiger is carry eggs and am wondering what's the best way to insure the shrimplets survive. I have a netted breeding box if I move the pregnant shrimp to that box will she be ok or will the stress cause her to miscarry.

Finally, I read MsJ's sticky and realized that the bee could breed with the tiger female. Although there is another tiger shrimp in the aquarium how likely is it that the shrimplets will be hybrdized?

I haven't bought a new plant in about 4 months. I'm thinking about Crinum natans but that's another thing. I checked it out, it has the lip on it's foot so I'm sure it's an apple snail not a random stow away.

Sponge over filter? I have a ehiem 2215 external can someone explain what you mean by sponge over filter. Obviously it sounds quite self explanatory but seeing as I've never tried...

Is there something I should buy?

I'm thinking about, well actually I'm going to set up a shrimp tank on Saturday or Sunday. I'm going to add clay rings, clay pot, giant hygro, and some java moss. I have a sponge filter with the flow regulated by a tap in the airline. Is there anything else I should consider?