Hard Water Fish Species – How to Choose the Right Fish for a Hard Water Aquarium

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Hard water aquariums can be challenging to maintain, especially if you’re not familiar with the different fish species that can tolerate these conditions.

Not all fish can tolerate hard water, so it’s essential to do your research before adding new fish to your tank.

This article will discuss the different types of hard water fish and provide tips on choosing the right one for your aquarium.

By following our simple guide, you’ll be able to choose the right fish for your hard water aquarium in no time!

What Makes Water Hard?

So, what exactly is hard water? Hard water is tap water that contains high concentrations of magnesium and calcium.

These minerals give the water a “hard” quality that can be measured with a TDS (total dissolved solids) or GH (general hardness) test kit.

How to Tell if Your Water Is Hard

The easiest way to tell if you have hard water in your home is to do a simple pH test.

Fill up a glass of room temperature tap water and add a few drops of universal indicator solution.

If the purple color changes from light lavender to dark blue, then your tap water probably has elevated levels of both magnesium and calcium, meaning it’s hard!

If you don’t want to go through the trouble of testing your water, you can always buy a TDS or GH test kit from your local pet store.

How to Choose the Right Fish for a Hard Water Aquarium

Believe it or not, just because a fish is native to hard, alkaline waters doesn’t automatically mean that it can survive in your aquarium.

Some species are far more sensitive to changes in water chemistry than others and may require stringent tank conditions to survive long-term.

To help you choose the right fish for your hard water aquarium, we’ve put together this list of 8 common freshwater species that are known to do well under these conditions.

8 Awesome Freshwater Fish Species That Prefer Hard Water

African Cichlids:

1. Electric Blue Cichlid

The electric blue cichlid is a beautiful fish native to hard, alkaline waters. This species is known for its bright blue coloration and aggressive behavior.

The ideal pH level for the electric blue cichlid is 8.0-8.4.

2. Eureka red peacock (Aulonocara jacobfreibergi)

The red peacock cichlid is a beautiful fish with bright red and blue markings. It’s a lively, playful fish that does best in a pH level of 7.0 or higher.

3. Emperor Cichlid (Aulonocara nyassae)

The emperor cichlid is a beautiful fish that can grow up to 12 inches in length. They are native to the lakes of Malawi and Mozambique in Africa, and they prefer water with a pH level of 7.5-8.5.

However, these fish are known for their aggressive behavior, and they should only be kept in tanks with other large, robust fish.

Central American Cichlids:

4. Convict cichlid

The convict cichlid is a freshwater fish native to Central America. It has a blue body with black stripes and can grow up to six inches in length.

This fish is a territorial predator and will defend its territory against other fish. The ideal pH level for the convict cichlid is 7.5-8.5.

5. Blood Parrot Cichlid

The blood parrot cichlid (or red parrot cichlid) is a brightly colored fish that can grow up to 8 inches in length.

It is a popular choice for hard water aquariums, as it can tolerate a pH level of up to 8.5. The blood parrot cichlid is a relatively peaceful fish, but it can be territorial towards other fish of the same species. It typically has a lifespan of 10-12 years.

6. Red Devil Cichlid

The red devil cichlid is a popular fish for hard water aquariums. They are brightly colored fish with a reddish-brown body and black markings.

They are relatively aggressive fish and should only be kept in tanks with other aggressive fish. Red devil cichlids do best in water with a pH level of 7.5 or higher.


The freshwater angelfish (Pterophyllum scalare) is a beautiful fish found in many tropical environments.

They are typically silver or black and have a long, flowing tail. Angelfish are schooling fish, so it’s best to keep them in groups of at least three.

They are relatively peaceful fish and can tolerate a wide range of water conditions, but they prefer water with a pH level of 6.5-7.5.

Freshwater Gobies:

7. Bumblebee goby (Brachygobius doriae)

The bumblebee goby is a small, brightly-colored fish that typically grows to around 2 inches in length. This fish is a bottom-dweller and is known for its playful personality. It prefers a pH level of 7.5-8.5 and can tolerate hard water up to 25 dH.

8. Zebra gobby (BrachygobiusRainfordi)

The zebra gobby is a small, brightly-colored fish native to Southeast Asia.

It is a hardy fish that can tolerate various water conditions, including hard water. The ideal pH level for this fish is 6.5 to 7.5.

They are active and schooling fish that typically grows to 2-3 inches. They are known for their playful behavior and are popular among aquarium enthusiasts for their beautiful coloration.

This list is not exhaustive, and many other species such as most Central American Cichlids, certain types of Rainbowfish and Killifish, Freshwater Gobies, and Brackish water fish also can live in hard water aquariums.

What Type Of Hard Water Does My Fish Need?

If you want to be sure about your fish’s needs, we recommend going with cichlids.

Cichlids native to Africa are usually found in very hard, alkaline waters that almost match our tap water.


Choosing the right fish for a hard water aquarium can be tricky, but it’s doable with a little bit of research.

In this article, we’ve highlighted some of the most popular fish species that thrive in hard water environments.

We’ve also provided tips on how to choose the right one for your tank.

So whether you’re looking for a flashy red devil cichlid or a peaceful angelfish, we’ve got you covered.


Is hard water bad for fish?

This brings us to whether or not hard water is bad for fish.

In most cases, the answer is no. Many fish species prefer hard water conditions to soft ones!

The key here is finding a balance between hardness and pH level. By following our guidelines above, you should be able to keep any freshwater fish in aquariums with moderate levels of both calcium and magnesium.

However, hard water can cause damage in some types of shrimp tanks. Because their shells are naturally more delicate, shrimp that live in hard water conditions will need extra care to thrive in your aquarium.

Does hard water hurt fish?

Hard water conditions can be harmful to certain fish species, especially when the water’s pH levels are elevated above neutral.

If your fish are native to soft water or acidic waters, adding more minerals into your tank will make them more susceptible to stress and disease.

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