Tiny shrimp that infest New York City’s tap water have reared their little heads again after an amateur biologist gave them a luminous glow.

The shrimp, harmless microscopic copepods, swarm through the drinking water of New York, Boston and Seattle, all cities exempt from U.S. filtering requirements, although the water is treated.

In fact, some sources contend the crustaceans, which eat mosquito larvae, may be the reason New York City’s tap water is notoriously good, at least to New Yorkers.

Toronto tap water, of which our city is equally proud, doesn’t come with a side of shrimp because the province requires all “surface water to be filtered,” says Jim Harnum, director of water treatment and supply for the city.

“This process removes most biological impurities, including copepods, so this is not an issue for the City of Toronto,” says Harnum.

It was last a big issue in New York City, before Wednesday’s posting, in 2004 because Orthodox rabbis questioned whether highly observant Jews should be drinking it.

At first the Orthodox Union, which certifies products as kosher in 68 countries, exempted the shrimpy water because the copepods weren’t visible, The New York Times reported in 2004 .

“What changed people's minds is when they saw a sample taken from a pond and saw them scooting around. Those are beyond the threshold,” said Rabbi Menachem Genack, the rabbinic administrator for the Orthodox Union.

Restaurants and bakeries and homeowners began filtering their water.

The copepods are impossible to eliminate and deliver health benefits to the reservoirs, the U.S. Department of Environment Production has said.