Someone filleted Brooklyn’s viral hydrant-puddle fish pond.

The vandal or vandals weren’t scared off by signs claiming the Bedford-Stuyvesant attraction was under surveillance and tore up the place Monday night — leaving residents and activists fishing for answers. 

The bizarre puddle-pond was hit at about 9 p.m. when the vandal or vandal’s took colorful gravel and hand painted stones and tossed around other decorations — killing about five fish out of the pond’s 100 gilled residents, locals said.

“[I found out] right as it happened … I just walked by and it was all destroyed,” block resident Devang Shah said. “It was really beat up, there were shells all over the place, the broom was broken. it was just a mess.”

Shah buried the fish that died overnight, he told The Post.

The aquarium at Tompkins Avenue and Hancock Street was made in a 2-inch sidewalk tree pit filled with water from a leaky hydrant, quickly gaining interested visitors but also drawing the ire of online activists and at least one veterinarian who has called the project “animal cruelty.”

Shah, who has lived on Hancock Street for over a decade, is an architect working to help expand the pond and turn it into a “landmark.” The pond’s creators are even raising $5,000 through GoFundMe to get a filtration system and ensure the fish can survive in the pond through winter.

But others would be more than happy to see the shallow “pond” gone for good and the fish relocated.

“Fish in these conditions are going to die one way or another,” veterinarian and Wet Pet Vet founder Ben Roosenbloom said. “If nothing else, they have virtually no chance of surviving the winter in water of that depth and volume, not to mention chemical run-off from salting the streets.”

Rosenbloom called the vandalism a “tragic but relatively unsurprising result” of the strange project.

“Rehouse them in appropriate ponds or large fish tanks,” the vet said. “These are, again, completely inappropriate conditions for the fish to be living in – and the vandalism is only one consequence of this.”

Neighborhood residents Emily Campbell and Max David “rescued” about 30 fish from the pond earlier this month, with the intention of finding them a new home with more appropriate living conditions.

Campbell said Tuesday that no one she knows “would ever have done (or approve” of the vandalism.

“It was just destructive, disrespectful to the fish and the community,” she said.

“Unfortunately, this kind of vandalism was predictable and one of the reasons I tried to rescue the fish in the first place … maybe these guys will see that the hydrant pond, while fun, wasn’t a safe place for the fish.”

Pond co-creator Hajj Malik Lovick was undeterred by the vandalism, saying he was at the site by daybreak to clean up. Lovick’s aunt — fondly known by neighbors as “Auntie” — said she was at the pond by 6 a.m. to rebuild, even adding dirt from her own yard.

“I just decorated here yesterday,” she lamented. “I was out here boohooing. I cried, but now it’s time to get busy.” 

While there are two surveillance cameras in front of the pond, Lovick was told they weren’t working, according to a management worker at the site.

“I’m not going to point any fingers either, though. I’m just focused on making sure the aquarium is OK,” he said.

The pond’s creators aren’t slowing down, having posted on social media advertising a school supplies, backpack giveaway and “goldfish adoption” event on Sept. 1. 

Shah told The Post the organizers are also hoping to install plexiglass and solar panels to ensure a more permanent structure for the pond in the coming months.

“It’s like the city is a canvas, kids can see it’s not just bureaucracy and governments,” Shah said. 

“It’s magic, it’s a form of magic in the city.”