The Best Aquarium Setup for Oscars: Fresh Water or Brackish?

You may see Oscars swimming in tanks with catfish or other brackish fish in a pet store aquarium. But don't assume Oscars do well in brackish water. Pet store operators will group fish by size and sometimes house brackish-water fish in freshwater with Oscars, not the other way around. Ocars, members of the Cichlid species, depend on meticulous water care and control for survival. Poor water quality can spell death for this species. They actually require double the filtration power and twice the number of water changes as most other freshwater aquarium fish.

  1. Tank Size

    • In captivity, Oscars can reach 12 to 16 inches in length and some weigh in excess of 2 lbs. The absolute minimum size for an aquarium to house one adult Oscar is 40 to 55 gallons, but OscarFishLover.com says 75 gallons is better. For two Oscars, plan on a 100-gallon tank or bigger. Attempting to house an Oscar in too small a tank is begging for extreme water issues and jeopardizing its life.

    Filtration

    • Oscars are particularly dirty fish; eating a sizeable amount of food, they also generate a copious amount of waste and consequent ammonia. OscarFishLover.com recommends purchasing two filters, each the size normally recommended for the tank size. Biological filters are preferable over mechanical or chemical models for Oscars.

    Heater and Thermometer

    • Water temperature for an Oscar needs to be maintained between 74 and 82 degrees Fahrenheit, so you need an aquarium heater and a thermometer. Water temperature that's too warm for too long will result in oxygen deprivation, which can hamper the fish's immune system and cause nerve and heart damage. When water is too cool, it exposes the fish to sudden chill, which will also hamper its immune system. An impaired immune system makes Oscars more susceptible to diseases, including the deadly ick.

    Feeding and Water Changes

    • The Oscar requires a minimum of 10 to 15 percent water changes each week. Also, watch the amount you feed an Oscar. Once-a-day feedings are all that these fish need. They should consume all the food offered within two minutes of feeding to prevent water quality issues. Weekly filter maintenance is also required.