Oscar Tank Mates That Actually Work (and What Gets Eaten)

Oscars are big, smart and hungry, and that shapes every tank mate decision. The simple rule most experienced keepers follow: if it fits in an oscar's mouth, sooner or later it goes in an oscar's mouth. Everything below starts from there.

First, the tank

One adult oscar needs about 75 gallons on its own. Once you add tank mates, plan on 125 gallons or more, with strong filtration and weekly water changes. Most "my oscar is aggressive" stories are really "my tank is too small" stories. Our oscar care guide and choosing a tank cover the setup, and our tank picks and filtration picks list gear sized for big fish.

Tank mates that usually work

• Severum: a South American cichlid with a calmer temper, similar water needs and a body too deep to swallow. One of the most common oscar partners for good reason.
• Geophagus (eartheaters): peaceful sand sifters that grow large enough to be left alone. Keep a group and give them a sand bottom. See also Geophagus altifrons.
• Large plecos: a common pleco or another big, armored species handles an oscar tank well. Skip small plecos that can be harassed. Our pleco care guide explains the size differences.
• Bichirs: armored, bottom dwelling and tough. Pick a larger species, since small bichirs can still fit in a mouth. Read the bichir care guide.
• Silver dollars: a fast schooling dither fish that stays out of the way. Add them at a size the oscar cannot swallow.
• Jack Dempsey: works in many large tanks, but it is a Central American with real attitude. Watch closely, especially if it pairs up.

Maybe, with a big tank and a backup plan

Stronger New World cichlids such as the green terror, jaguar cichlid or red devil are sometimes kept with oscars, but these fish can bully or injure an oscar, which is a fairly gentle giant for its size. Only try it in a very large tank, add fish at similar sizes, and have a spare tank ready.

Fish that get eaten or bullied

• Small community fish: tetras, guppies, rasboras and small barbs are snacks.
• Dwarf cichlids: rams, apistos and kribensis are too small and too timid.
• Slow, long finned fish: angelfish and fancy goldfish tend to get nipped or eaten, and goldfish want cooler water anyway.
• African cichlids: mbuna and peacocks want hard, alkaline water and fight in a very different style. Our African vs American cichlids guide explains why mixing usually goes badly.

How to add tank mates without a war

1. Quarantine first. A new fish that brings disease puts your oscar at risk. See quarantine.
2. Add tank mates young, together, or before the oscar settles in. An oscar that has owned the tank alone for years is less forgiving.
3. Rearrange the rock and wood when you add someone new, so nobody holds a claimed territory.
4. Break lines of sight with large driftwood and smooth rock. Our rock and decor picks help here.
5. Feed well and keep the water clean. A messy, crowded tank raises tempers. A good large cichlid pellet and a steady water change routine go a long way.

Every oscar is an individual. Some live peacefully with a full tank, and a few will not share at all. Read our compatibility guide before you buy, and if you want a second opinion on your stocking list, ask the community.

Frequently asked questions