Nobody likes a night interrupted by blinding artificial light, least of all the fish who make their home on coastal reefs.

As a new study published in the journal Current Biology found, even a faint amount of artificial light during quiet hours is enough to cause a fish to have a crappy day.

Specifically, the researchers found that artificial light from coastal settlements is associated with major fluctuations in behavior and physiology of damselfish schooling in the Red Sea. In particular, fish exposed to human light pollution experienced disrupted sleep, leading them to act aggressively and eat at strange hours of the night. In other words, a bad night’s sleep seems to make you cranky whether you have legs or fins.

Fish, however, can’t really control the light that leaks into their environment from ports and coastal roads — a major source of artificial illumination leaking into marine habitats.

After just a few days of observation, fish exposed to nighttime light demonstrated all the tell-tale signs of sleep deprivation, which researchers suggest may cause lasting damage not only in fish, but in the environments they interact with.

“Coral reefs depend on tightly connected biological interactions,” Oren Levy, one of the study’s co-authors and a researcher at Bar-Ilan University said in a press release. “If artificial light is affecting both corals and the fish that depend on them, the consequences could ripple throughout the reef ecosystem.”

To make life a little bit more bearable for our underwater friends, the study authors call for smarter coastal lighting practices, including a reduction of unnecessary nighttime lighting, and directing light beams inland, away from the water.

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