Predators of stickleback fish include birds such as herons and cormorants, as well as larger fish like pike and bass. Additionally, mammals like otters and raccoons are known to feed on stickleback fish.
shrimp, insects and sometimes other fish
No, the snail wouldn't eat it because they do not eat other animals, and because he is not fast enough.
they eat algae and dead fish
alerge
No, they will not. The dragon-fish can eat the ghost shrimp and the snail, and the crab will try to eat anything he can catch.
they have to
Brook stickleback fish live to about one to two years occasionally three years.
yes, why not!
External, like most fish.
If the snail(s) are still transparent then if the fish see it they will most probably eat it because its shell is not hard enough to protect it.
If the fish can find the eggs and/or babies they will eat them.