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How Many Green Terrors Can Live In a 55 Gallon Tank?

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By Lindsey Stanton

green terror

Although they are called green terrors, these are some of the most colorful fish from the cichlid species and, in fact, one of the most colorful fish in general. The best specimens will display literally every color under the rainbow. These are cichlids, and they have definitely earned their moniker, “terror.”

So, based on this, you might be wondering how many green terrors in a 55-gallon tank. A single green terror cichlid needs at least 35-40 gallons of tank space therefore you can house one in a 55-gallon tank. If you plan on keeping a mating pair together, somewhere around 75 or 80 gallons should be fine.

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How Many Green Terrors Should I Get?

At the most, you should get two green terrors. The reason for this is because of their aggressive and territorial nature. They aren’t really schooling fish, so they don’t like being in groups very much, and they are far too territorial to be kept in large groups.

Can 2 Green Terrors Live Together?

It is recommended to keep a single green terror cichlid, or to keep a mating pair, so a male and a female. What is surprising is that female green terrors are usually more aggressive than the males, although the males are still pretty mean. Therefore, the maximum amount you should keep together is two, and they should be male and female. Males and males, and females and females, won’t get along.

Minimum Tank Size for Green Terrors

green terror cichlid
Image Credit: Photofenik, Shutterstock

Green terrors can grow up to a foot or 12 inches in length, which is quite large, and which automatically means that they need a fairly large tank. However, due to their aggressive and territorial nature, they actually need more space than most other fish, particularly if there is more than one or other tank mates.

The general guideline of 35-40+ gallons per fish is advisable.

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Green Terror Housing Requirements

The size of the tank and how many green terrors you can keep together are both important, but you do also need to know about other general green terror housing requirements, so let’s go over these right now.

Water Temperature

Green terror cichlids need their water to be moderately warm, but not super warm. They prefer it to be between 68 and 77 degrees Fahrenheit, with that lower number actually being lower than room temperature. That being said, ideal is if you can keep the tank around 72 degrees, so just around room temperature.

However, chances are that you will still need an aquarium heater, or else you won’t be able to maintain that temperature, plus a decent aquarium thermometer probably wouldn’t hurt either.

If you are in doubt, it’s better to have a heater on standby than to allow the water to get too cold.

Image Credit: Flups, Shutterstock

Water Hardness

Green terror cichlids are not too picky when it comes to water hardness, as they can survive in soft and moderately hard water, although not too hard.

The water hardness rating for these fish should be between 5 and 20 dGH, with 5 being very soft and 20 being moderately hard, although not overly hard. Therefore, you will likely need a water testing kit as well as a water softener to ensure that it’s not too hard for survival.

Water pH

Green terror cichlids are also not too picky about the water’s pH level. They can handle a pH between 6.5 and 8.0, with 6.5 being slightly acidic, 7.0 being neutral, and 8.0 being somewhat alkaline.

It’s best if you can keep the water just above 7.0 or slightly alkaline. You will probably want to invest in an aquarium pH testing kit to ensure that you are maintaining the proper pH level.

man conducting ammonia test in front of freshwater aquarium
Image Credit: Ladanifer, Shutterstock

Filtration & Aeration

Green terrors are quite sensitive to parameter changes and to dirty water. Plus, they are messy and voracious eaters that produce lots of waste. Therefore, you do need a strong and efficient filter, with an external canister filter being the best option.

You want to ensure that the filter can process around four times the total water volume in the tank per hour. For an 80-gallon tank, you want a filter that can process around 320 gallons of water per hour.

Moreover, you do need a filter with efficient mechanical, biological, and chemical filtration. The current for these fish should be moderate. If you have a good filter and a good amount of plants in the tank, you should not require any additional aeration or oxygenation.


Green terror cichlids do not like bright light, but you do still need to mimic natural daylight. Therefore, a fairly dim aquarium light will do fine here. Just beware that you will need to get plants that can survive with fairly dim lighting.

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Image Credit: Nor Gal, Shutterstock


In terms of the substrate, you should be using soft and fine grain sand. You should not be using small rocks or gravel as substrate.

Green terrors have been known to eat aquarium gravel, which ends up causing serious digestive issues and sometimes even death. Sand is the way to go.


When it comes to plants, things like anubias, java ferns, and anything else that can be used as a floating plant is ideal. Green terrors will most likely uproot rooted plants, so these are not ideal.

If you do go for rooted plants, they must be very hardy with super-strong root systems, or else they will not survive. That being said, green terrors do like to have some cover from above, so some plants are required.

java fern
Image Credit: Joan Carles Juarez, Shutterstock

Rocks & Deco

Adding some rocks and driftwood to the mix is recommended here, just to help mimic their natural environment. Moreover, some decorations such as these can help create some natural barriers in the tank in an attempt to reduce territoriality.

Tank Mates

Green terror cichlids should only be kept with other fish of similar size and temperament. Anything smaller or less aggressive will get bullied, harassed, and likely killed.

Some good green terror tank mates include silver dollar fish, pacus, large catfish, large bleeding heart tetras, and other large cichlids.

two bleeding heart tetra adult males
Image Credit: Aleron Val, Shutterstock



Are Green Terrors Easy to Care for?

Green terror cichlids are definitely not the easiest fish to care for. They need lots of space, they don’t do well in community tanks, they are territorial and aggressive, and they have some pretty specific tank requirements that need to be met.

How Long does it Take for Green Terrors to Reach Full Size?

It will take somewhere under 1 year for these fish to reach their full size.

Are Green Terrors Aggressive?

Yes, green terrors are very aggressive and are likely to attack many other fish, especially smaller ones.

Can You Keep Oscars with Green Terrors?

Yes, you can keep Oscars and Green Terrors together. Both are large and aggressive. They may fight each other, but both should be able to hold their own.

Aggressiveness can be avoided by providing ample tank space and lots of natural barriers within the tank.

oscar fish close up
Image Credit: madcat13shumbrat, Shutterstock



The bottom line is that while Green Terrors are very beautiful, it does take a seasoned aquarist to care for them and they need to be housed with a big tank so they have a good environment to thrive in.

Featured Image Credit: Marek Velechovsky, Shutterstock

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