Neon Tetras

Do Neon Tetras Like Hard Water in Aquariums?

5 min read

Neon Tetras are a favorite pick for aquarists – if you take a look at these magnificent creatures, it is easy to see why.

Aquarium keepers are partial towards fish with bright colors, and the neon tetra stands out with its brilliant iridescent stripes of blue and red. A shoal of neon tetras in your aquarium will be quite a sight, displaying arrays of blue and red lines.

Of course, with any aquarium fish you need to make sure you meet their requirements – one concern you may have is this: do neon tetras like hard water?

We’ll answer that in this post and also look at the ideal neon tetra water hardness. While we are at it, we will also discuss the other neon tetra requirements such as pH, temperature, and tank size.

Let’s get started.

Do Neon Tetras Like Hard Water?

Neon Tetras

This is a good question to ask because it is very relevant to neon tetras.

The short answer is no, neon tetras do not like hard water. They prefer soft and slightly acidic water, which mimics their natural habitat in the blackwater and clearwater streams in the Amazon basin.  

The recommended water hardness for neon tetras is between 2-10 dGH, while it can reach 15 dGH without causing any serious issues.

In other words, neon tetra water hardness ppm should be between 35.8 and 179. It is always wise to test the water before you introduce any fish.  

So does that mean if you want neon tetras, hard water is a complete no? Well, not really; read on and learn more.

Can Neon Tetras Tolerate Hard Water?

We now know that neon tetras prefer soft water, but the real question is can they tolerate hard water?

It seems that they can, as long as it’s within a tolerable range. We have seen that they can tolerate up to 15 dGH, which can be described as medium hardness.

Neon Tetras

That being said, extended exposure to water that is too hard is not going to be good for your neon tetras, since we know for a fact that they prefer soft water.

Captive-bred tetras are more likely to tolerate hard water as they get used to conditions in an aquarium. On the other hand, wild tetras may go into shock if they are suddenly introduced to hard water.

So if you are going to subject your neon tetras to hard water, at least acclimate them slowly to avoid the risk of adverse reactions.

Why is Hard Water Bad for Neon Tetras?

If you happen to be an inquiring mind, you may want to know why hard water is not suitable for neon tetras.

It turns out there are a number of ways hard water can adversely impact your fish and aquarium.

The first issue with hard water is a parameter known as Total Dissolved Solids (TDS), which should be self-explanatory. This is a measure of dissolved solids such as calcium and magnesium (the main culprits behind hard water).

You may know this already: a fish absorbs water through its skin as well as its gills. That means the dissolved solids also enter the fish’s system.

Now, the solid particles are a toxin as far as the fish is concerned, so its kidneys work overtime to get rid of the particles.

Kidneys of fish that are used to hard water know how to handle this influx of solid particles, but if a fish is suddenly inundated with high amounts of solid particles, it could lead to kidney failure and even death. Anything above 150 TDS is asking for trouble in a neon tetra aquarium.

Another complication is that hard water is intrinsically linked to water pH – the harder the water, the higher its pH tends to be.

So hard water may be good for fish that prefer some alkalinity, but not for neon tetras that like acidic water.

Neon Tetras

Furthermore, it will be difficult to breed neon tetras in hard water. Bacteria and fungi have a good time in hard water with a high pH and can destroy the eggs.    [

Lastly, hard water leads to less available carbon dioxide as the carbonate salts latch onto CO2. While this may not affect your neon tetras directly, plants in your aquarium may struggle, and plants are a major part of the appeal of any tank.

What Are The Other Neon Tetra Tank Requirements?

We have looked in detail about the required water hardness for neon tetras; it’s time to look into other required neon tetra water conditions.

Neon Tetra Temperature Requirement

Being tropical fish, neon tetras like their water to be warm, although they can withstand some cold. You should aim for a temperature of 68-82 °F (20-28 °C).

pH Requirement

As we have seen, neon tetras prefer slightly acidic water and can tolerate acidity really well. They can do well in the range of 4-7.5 pH. If you want to breed them, however, the pH should be less than 6.5.

It would be convenient to maintain a pH of around 7 in your aquarium.

Neon Tetra Tank Size

Neon tetras are quite small in size, but since you are not going to get just one, you need to set up the appropriate tank size. You need at least 10 gallons to keep neon tetras.

So how many neon tetras in a 10 gallon tank? You can have about 10 neon tetras in a 10 gallon tank. If the water is maintained efficiently, you can push this number up.

Remember, it is about bioload – the amount of waste-producing creatures you have in your tank.

Tetras are a shoaling fish and should be kept in groups of at least 6 – ideally, you should get around a dozen.

Aquarium Plants

Neon tetras love densely planted aquariums; it is reminiscent of their natural habitat in the Amazon basin.

The plants provide hiding spots for your tetras to dart in and out. Neon tetras are shy and easily scared, so it is important to provide them with ample hiding spots.

Aquarium plants provide a host of other benefits as well, such as oxygenating the water, removing harmful chemicals, and reducing the growth of algae.


To sum up, neon tetras prefer soft and slightly acidic water; you should try to maintain those conditions for your tetras to be healthy and have a long lifespan, especially if you are hoping to breed them.

Sometimes, soft water is not easily available for you; that’s alright – neon tetras CAN tolerate medium-hard water. Just make sure you don’t exceed the maximum hardness or abruptly introduce your fish to hard water.

Likewise, you should maintain the other optimal neon tetra living conditions such as temperature, pH, tank size, etc.

That’s it, with proper tank conditions, you can just sit back and watch your shoal of neon tetras dart around in your tank, adding a dazzle of colors to your aquarium.

Thanks for reading.


Written by:

Pet Aquariums

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