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How to Set Up an Oscar Tank

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Oscars (Astronotus ocellatus) are popular cichlids well-loved for their amiable personalities. Also called marble cichlid, velvet cichlid, or tiger Oscar, these freshwater fish species can grow fairly large thus they will need an adequately-sized tank. In the wild, they can reach a length of 18 inches and may weigh more than three pounds, when mature.

Oscars originate from the Amazon River, in areas where there is lush aquatic vegetation. In order for your Oscar to live a full and healthy life, you need to create an aquatic environment that mimics their original habitat. Oscars do not get along well with other cichlids and don’t tolerate cool temperatures. They can also get territorial or combative.

Tank Size

In captivity, Oscars can grow to about 10 inches in length thus the minimum aquarium size recommended for one Oscar is about 55 gallons. Ideally, a 75-gallon tank is best for one adult Oscar. Since Oscars love to eat, your tank will certainly have a lot of waste, resulting in a large bioload. Thus, you need to put in a good filtration system to help maintain ideal water quality. Many aquarists recommend combining canister filters with a hang-on-back (HOB) filter. If you keep your Oscar in a small tank, you will be facing problems keeping fish aquarium water in good condition. Poor water conditions are important predisposing factors for illness, and even death, of the tank inhabitants.
tiger oscar

Setting up the Aquarium

  • Setting up an Oscar tank follows the same procedure applied in most freshwater species. The first step is to make sure that all the equipment and ornaments are washed before being placed in the aquarium.
  • If you are using an under-gravel filter, place it first on the bottom of your tank.
  • Add 3-5 inches of substrate. The depth allows enough support for decorations and aquatic plants. If you are using sand, be sure to use a pre-filter on the filter intake to prevent find sand from entering the filter and destroying it.
  • Condition the tank water. This is achieved by allowing tap water to stand for 24 hours or using a water conditioner to get rid of contaminants.
  • Conditioned water is then poured into the tank. Make sure to do it gently to prevent disrupting the gravel substrate. You can also put a bowl on the bottom of the tank and slowly pour the water directly into the bowl to avoid stirring up the substrate.
  • Once the tank is half-full, you can now add some tank ornaments, plants, and rocks. Make sure that they are securely anchored to the tank substrate. Limit putting in lots of decorations since these can hinder the movement of the fish.
  • Oscars are known jumpers thus you need to provide a cover or lid for your tank.

Because Oscars are highly sensitive to temperature fluctuations, have an aquarium thermometer so you can easily keep track of the tank’s temperature. The ideal temperature for Oscars range between 74-81 °F, with the ideal temperature around 77 °F.

Coming from a tropical habitat, Oscars need warm water. You may need to put in an aquarium heater to keep the water warm. If you are considering using a heater, get an in-line heater that can be linked to the canister filter so aquarium water is heated as it is returned to the tank. If you have a submersible or hang- on heater, make sure that it is shatter-proof, since Oscars can be quite destructive.


By: Peter Hartono

Featured Image: Via Santhosh Varghese