How to Breed Pajama Cardinalfish

Pajama cardinalfish are small marine fish, only growing to about three-inches long. However, they are strikingly patterned and brightly colored. They often sport green, blue, yellow, and red stripes, patches, or spots. These fish are hardy and are known to tolerate a range of water conditions. They are also usually non-aggressive. These two facts means that pajama cardinalfish are easy to care for and easy to breed. They often spawn with little or no prompting, when correct water conditions are provided.

Things You'll Need

  • Marine aquarium
  • Aquarium decorations
  • Hydrometer
  • Water testing kit
  • Thermometer
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Instructions

    • 1

      Set up a marine aquarium where only the pajama cardinalfish will be kept while they breed. This aquarium should be 30 gallons or larger in size. The pajama cardinalfish, can become quite aggressive when they are ready to breed. They may injure other aquarium inhabitants, so it's best to house them separately.

    • 2

      Place some aquarium decorations, such as rocks or cave structures, in the aquarium. These decorations provide hiding places, and will make the cardinalfish more comfortable. Comfortable fish are more likely to breed.

    • 3

      Monitor the specific gravity of the water. Specific gravity relates to the salinity of the water in the aquarium and can be measured using a hydrometer. Pajama cardinalfish prefer a specific gravity between 1.020 and 1.025. Freshwater or aquarium salt can be added to raise or lower the specific gravity.

    • 4

      Test the water with a water-testing kit to determine the pH level of the water. Pajama cardinalfish are most comfortable with a pH level between 8.1 and 8.4. Use pH additives to bring this level up or down, if it's not correct.

    • 5

      Ensure the water temperature stays between 72 and 82 degrees Fahrenheit. Pajama cardinalfish are tropical fish and prefer warmer temperatures.

    • 6

      Place a group of about five cardinalfish in the aquarium. It's usually difficult to determine the gender of pajama cardinalfish, until you see them breeding, so using a group of fish ensures you will have at least one male and one female fish. The male and female fish will form breeding pairs after they become comfortable with their surroundings.

    • 7

      Wait for the pajama cardinalfish to breed. This will happen soon after the fish form their breeding pairs. The female fish lays the eggs, and the male picks them up and broods them in the mouth for about a week, until the eggs hatch.