Detrius worms. Your shrimps and snails won’t eat them, but they will go away eventually. They are always in most tanks but in low numbers. Either something died in your tank recently or you overfed, allowing them to captivate on a new food source and boom in population.
TheArabCanadian 
Detrius worms. Your shrimps and snails won’t eat them, but they will go away eventually. They are always in most tanks but in low numbers. Either something died in your tank recently or you overfed, allowing them to captivate on a new food source and boom in population.