How Many Orandas Can Go in a 100-Gallon Tank?

Oranda fish are a type of exotic goldfish. No wild populations exist, as they were specially bred from wild carp (Carassius gibelio) as an ornamental species. Their most notable feature is the wen, or hood, that grows on top of their heads. These fish usually grow to between 6 and 7 inches in length, but have been known to reach 15 inches; it's important you don't overcrowd them.

  1. Oranda Numbers

    • When housing multiple orandas, you should allow between 20 and 30 gallons for your first fish and then 10 gallons for every additional one you wish to keep. This means that you can keep 8 or 9 orandas in a 100-gallon tank. It's important not to house too many, because their waste will build up, which could make your fish prone to illness or infection. They also need plenty of room to swim around. If you don't want your fish to breed, keep them in a single-sex group, but otherwise a mixed group is fine.

    Other Tank Mates

    • As peaceful fish, you don't need to worry about your orandas bullying or attacking other kinds of fish in the tank. However, if you choose to keep orandas with other fish species, you'll need to ensure they're gentle, they don't fin-nip and they thrive in water conditions that orandas thrive in. The number of other fish you can keep in your 100-gallon tank with your orandas will depend on their size and individual space needs. Consult your aquarium supply stockist or fish breeder if you're unsure.

    Tank Setup

    • When setting up your 100 gallon tank for orandas, start by providing a medium-size gravel substrate. Ornaments, rocks or driftwood with sharp or protruding edges can damage their long fins, so place just a few smooth rocks or logs, if any. Plants are the safest option to provide your fish a little bit of cover. However, these fish are known diggers, so place silk artificial plants instead of live ones.

    Water

    • The water conditions in your orandas' tank are important. Although they're goldfish, they're not true cold water fish and do require a heated tank. Keep water temperatures between 65 and 72 degrees Fahrenheit, pH between 6.0 and 8.0, and hardness between 5 and 19 degrees of general hardness. Your tank will need a good biological filtration system to keep the water clean and to provide a moderate amount of water movement.

    Tank Maintenance

    • Once your tank is set up with your orandas in it, you'll need to maintain it to keep your fish happy and health. Change one-quarter to one-third of the water in the tank once a week. If you notice a buildup of algae, clean the inside of the glass with an algae scraper. You can also clean the substrate in the tank using a gravel vacuum.