1. Water Quality: Poor water quality, such as high levels of ammonia, nitrites, or nitrates, can cause fish to stay near the bottom where they perceive a higher concentration of oxygen. Check the water parameters and perform regular water changes to ensure optimal water quality.
2. Stress: Stressful conditions, such as overcrowding, aggressive tank mates, sudden changes in water parameters, or transportation can lead to fish staying at the bottom. Provide appropriate hiding spots, ensure suitable tank mates, and avoid rapid changes in the environment to reduce stress.
3. Illness: Some fish diseases, such as swim bladder disorder, bacterial infections, or internal parasites can affect a fish's buoyancy and cause them to sink to the bottom. Observe the fish for any visible symptoms and seek treatment if necessary.
4. Resting Behavior: Some fish species naturally spend time resting on the bottom, particularly bottom-dwelling species like catfish or certain loaches. This is their normal behavior pattern, and they may prefer to stay at the bottom to feel secure.
5. Feeding Habits: Some fish have bottom-feeding habits. If your fish is searching for food at the bottom of the tank, it might be attempting to pick up leftover food or find small organisms like crustaceans or worms that reside in the substrate.
6. Acclimation: When introducing new fish to an aquarium, it's not uncommon for them to remain at the bottom of the tank initially. This behavior may be due to the stress of being in a new environment and will often subside as the fish becomes more comfortable.
If a fish stays at the bottom of the aquarium for an extended period and shows other unusual behavior or symptoms, it's essential to closely monitor the fish and identify any underlying causes. If necessary, consult with an aquatic veterinarian or experienced aquarist for proper diagnosis and treatment.