Why Did Adding New Fish to an Aquarium Cause the Water to Become Cloudy?

There are a number of reasons why adding a new fish to an aquarium can turn the water cloudy. Putting a new fish into an aquarium is stressful both for the new fish and for the fish already present, and their physical reaction leads to the cloudiness. Some action before and after adding the fish can lessen this reaction.

  1. Stress

    • Organic matter is the main source of cloudiness in a fish tank. It's caused by blood, excrement and bacteria that can also make the fish sick. When a new fish is introduced, aggressive and stressed residents (or an aggressive newcomer) may launch attacks that lead to an increase of those organic matters, and thus an increase in the cloudiness.

    Food

    • A fish can go into shock if it is added into an aquarium too soon, and this may cause it to stop eating any of its food. Uneaten fish food can float in the water or settle to the bottom of the tank, where it begins to decompose. This decomposing material can cause the aquarium to turn cloudy.

    Water Level

    • An extra fish uses space, filters water and excretes as much as the fish already in the tank; adding a new one increases the amount of waste without increasing the amount of water available for the fish population. This can also lead to competition for space and resources among the fish.

    Stores

    • Pet stores may have chemicals or bacteria that are not present in a homeowner's tank. When the new fish is placed in the water, these chemicals and bacteria can be released into the water and cloud it up. Keeping the new fish in its own tank or purchasing a small tank to use for several days can reduce this problem. The fish will shed much of the store bacteria and chemicals in that tank first.

    Cleaning

    • Regular cleaning of a fish tank is essential for the health of fish, and it becomes especially important when a new fish has been added, as all of the fish are likely to be stressed by the presence of a new individual in their habitat. Plan a doing a complete cleaning within a few days after putting in a new fish. That should keep the cloudiness from building up to where it becomes a problem.