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Fish can be wonderful pets, amazing installations of aquatic art you can enjoy and even interact with. They can become skittish, however, and when your fish start hiding, you can't enjoy them nearly as much. By understanding why your fish are hiding, you can take steps to make them more comfortable and confident in your aquarium.

The Nature of Fish

Fish are prey species, particularly the smaller varieties that are popular in aquariums. Even more aggressive fish are often preyed on by larger fish in the ecosystem. To protect themselves, fish will instinctively hide when they are uncertain, frightened, stressed or uncomfortable. Having a safe place to retreat provides comfort and security, and greatly improves a fish's chance of surviving in the wild. While aquarium fish are rarely at risk from lurking predators, they have never lost their self-preservation instincts and will frequently hide in any uncertain situation. There are ways, however, that aquarium keepers can help their fish feel safe and come out of hiding.

Why Fish Hide

There are many different reasons why even the boldest aquarium residents may suddenly start hiding, including…

• Newcomers – If a fish was bold in the pet store tank but starts hiding when introduced to a community tank, it is simply uncertain in its new, unfamiliar territory. Even long-time residents may hide when a new fish is introduced until they are all comfortable with their personal territories. Within a few days, the fish should feel more secure with each other.
  
  
• Bullies – A fish that is bullied by a larger, more aggressive fish will seek out hiding places to protect itself from unwanted attention. Separating fish that are more aggressive from passive species can help reduce this type of hiding. Another option is to rearrange the tank's décor to disrupt established territories so every fish has to find its own niche in the tank again.
  
  
• Loneliness – Fish that naturally gather in larger communities may start to hide if they feel isolated or alone in the tank because they no longer have the protection of a larger school. Adding more compatible species to the tank and increasing the number of fish can help these species feel safer swimming into the open.
  
  
• Open Space – If a large tank has too few decorations and too much empty space, even bold fish can start to hide out of anxiety and uncertainty. Open spaces offer more room for potential predators to strike, with no cozy spaces to retreat to safety. Adding more hiding spaces to the tank can encourage these fish to swim about more freely.
  
  
• Environmental Changes – Anything that alters a fish's environment can spook the fish into hiding. This can include sudden water changes, temperature shifts, pH changes or chemical imbalances. As the tank stabilizes at the optimum environmental conditions, the fish should lose their shyness and stop hiding as much.
  
  
• Overcrowding – If a tank is too small for all its residents, fish may start hiding to avoid too much attention from their neighbors. This can also increase territoriality and aggression, causing more passive fish to hide even more. Switching to a larger tank or reducing the fish population can make all the fish more comfortable.
  
  
• Currents – Very small fish may be uncomfortable in strong currents from a new filter, oxygenator or bubbler, and may start hiding to keep away from the unnerving water movements. Adjusting the currents can help these fish feel more comfortable so they can explore the whole tank again.
  
  
• Threats – If fish perceive a threat, they will immediately retreat to a hiding space. This could be loud noises in the room, or people or pets moving near the tank. Keeping fish in a quiet area can encourage them to move about more freely, or else keep them acclimated to simple movements nearby so they get used to the stimulation and it won't worry them.
  
  
• Illness – When fish start to feel sick, they may seek out hiding places to hide any weakness from potential predators and bullies. If a fish starts hiding suddenly, it is best to try and get a good look at the fish and note its eating and other behavioral habits to ensure the entire community does not become infected.

Regardless of the reason, it is important to note that some fish just naturally hide more than others. Even in a bold species, different fish have different personalities and some may seek out hiding spaces more frequently.

Helping Your Fish Hide

Because hiding is a natural instinct for fish, offering more hiding places in your aquarium can help your fish feel more secure and at ease. Extra hiding places can even help shy fish feel bolder as they come out to explore, and additional obstacles in the tank provide enrichment to keep fish active and entertained. Consider adding extra plants, driftwood, rocks, caves, tunnels, and structures to give your fish more places to hide, and you'll be surprised at how much more you see of them.