Do Shrimp Sleep? A Look At Their After-Dark Adventures!

Shrimp don’t sleep in the traditional sense but enter phases of quiescence or lethargus multiple times a day, during which their activity levels are reduced.

Unlike humans, who are mostly active during the day, many shrimp species are cathemeral, exhibiting sporadic activity throughout both day and night.

Do Shrimp Sleep?

Ammano Shrimp And Cherry Shrimp In My Tank
Ammano Shrimp And Cherry Shrimp In My Tank

Shrimp don’t sleep in the traditional sense but enter phases of quiescence or lethargus multiple times a day, during which they exhibit low activity levels.

It’s common for arthropods and nematodes to adjust their activity based on food availability, leading to seemingly random periods of activity throughout the day and night.

There’s ongoing debate about whether shrimp exhibit quiescence or lethargus, given their similarities.

Lethargus is actually a type of quiescence, so both arguments are technically correct. The key takeaway is that shrimp don’t sleep.

Are Shrimp Nocturnal Or Diurnal?

An Amano Shrimp And Cherry Shrimp In My Tank At Night
An Amano Shrimp And Cherry Shrimp In My Tank At Night

All shrimp can be classified as cathemeral, meaning they display sporadic activity during both day and night rather than being strictly diurnal or nocturnal.

However, some shrimp may exhibit heightened activity at specific times, influenced by the availability of their primary food source or the presence of potential predators.

After these periods of increased activity, shrimp return to a quiescent state, waiting for the next feeding opportunity instead of sleeping.

This is why shrimp in aquariums appear active throughout the day: the abundant food supply and lack of predators allow them to graze on algae and biofilm without interruption.

In my own experience, my shrimp seemed to feed on the algae continuously, and within two weeks, all the algae on the java moss had been consumed.

Why Do My Shrimp Behave Differently At Night?

Amano Shrimp And Cherry Shrimp Grazing In My Tank
Amano Shrimp And Cherry Shrimp Grazing In My Tank

Some shrimp can display higher activity levels at night due to elevated CO2 levels in their tank causing pH fluctuations.

These changes typically occur in planted tanks or tanks with large amounts of algae as part of the natural CO2 cycle.

This phenomenon can lead some people to believe their shrimp are nocturnal, but the increased activity is actually due to mild irritation from pH changes.

At night, the lack of light causes live aquarium plants to cease photosynthesis while continuing their natural respiration. As a result, oxygen levels decrease and CO2 levels increase, though usually not enough to cause serious problems for shrimp or fish.

To help maintain proper oxygen levels, I always keep a sponge filter in my tanks to ensure that my fish and shrimp can breathe comfortably.

The main reason your shrimp are more active at night is due to the increased CO2 levels temporarily lowering the tank’s pH. Even if the pH shift remains within the recommended range for your shrimp, the rapid change can cause mild irritation, leading to increased activity.

How Does Light Affect Shrimp Behavior And Activity Levels?

Shrimp In One Of My Aquariums
Shrimp In One Of My Aquariums

Bright lighting can cause your shrimp to hide or reduce their activity levels compared to moderate lighting conditions.

This is a common misconception that leads people to believe their shrimp are nocturnal, when in fact the tank lighting is simply too intense for them.

Lighting intensity is only part of the issue; the photoperiod, or duration the lights are on, also plays a role. Many people with planted aquariums keep their lights on for six to eight hours, which is generally suitable for most shrimp.

If your tank lights are on for more than eight hours and you notice your shrimp hiding and inactive during the day, try reducing the photoperiod.

I use a budget-friendly Nicrew C10 light with its standard 24/7 lighting schedule, and my shrimp are thriving.

Final Thoughts

Shrimp do not sleep in the conventional sense but enter states of quiescence or lethargus with reduced activity levels.

The majority of shrimp are generally cathemeral, displaying random spurts of activity throughout the day and night rather than prefering to be fully diurnal or nocturnal.

Environmental factors like CO2 levels and lighting conditions in an aquarium can influence the behavior of shrimp, but they typically adapt well to moderate lighting with a six to eight-hour photoperiod.

Understanding these nuances can help aquarium enthusiasts create a more suitable and comfortable habitat for their shrimp.