Adding Salt to Guppy Tank – The Complete Guide

Many aquarists like adding salt to the guppy tank due to the chemical’s beneficial effects on the environment. Salt functions as an environmental regulating substance and medication, depending on the context.

But what exactly are the immediate effects of adding salt to your guppy tank, and is it safe? Also, how do you know when you’ve poured too much salt, and how will it affect guppies?

Today, we’ll answer all these questions and many others to shed light on a regular practice in the aquarium business.

Can You Put Salt in Guppy Tank?

Yes, but only in a guppy tank. Adding salt to your tank water isn’t always good, especially if you’re keeping freshwater fish. Fortunately, guppies are used to living in brackish water, which isn’t fresh but isn’t marine water either. It’s a mix of both but with moderate salt content.

With that in mind, yes, it’s safe to use salt for your guppies, albeit in measured amounts whenever necessary. But why do aquarists use salt for their guppy tanks, and in what context?

Why Aquarists Use Salt in Fish Tank?

There are 3 core benefits to using salt for your guppy tank:

– Preventing and Treating Viral Infections

In some cases, increasing your tank water’s salt levels will kill some bacteria, fungi, and viruses that could target the fish. However, this is only a minor effect since most of these pathogens are resistant to salt. Especially in low quantities, since you can’t use too much salt anyway.

However, the real benefit comes via the salt’s effects on your fish’s biology. It appears that salt promotes the production of body mucus which increases the guppy’s resistance to external parasites. This is especially useful in case of housing guppies with compromised immune systems or that are recovering from various diseases.

Salt is also useful as medication when treating bacterial, fungal, or parasitic infections. The added salt helps guppies produce more mucus and speeds up their natural healing processes.

– Supporting the Osmosis Process

Osmosis refers to the process of water moving from an area with low fluid concentration (the fish’s body) to one with higher fluid concentration (tank water.) This definition pretty much explains what osmoregulation is. The latter refers to fish actively seeking to balance out their bodies’ salinity levels with those of the surrounding water.

Letting out too much salt via urine and skin will potentially kill them, and the same can happen the other way around.

Since they’re brackish-water fish, guppies will let out more salt than they will take in. So, keeping them in a pure freshwater environment isn’t quite ideal. Adding some salt into their environment is great for allowing them to self-regulate their salt content.

Guppies can experience osmotic shock if the salt content in the tank fluctuates too abruptly. So, always consider adding a safe amount of salt, as recommended for your fish.

– Preventing Nitrate Poisoning

Nitrates aren’t as dangerous to your guppies compared to ammonia and nitrites. That being said, nitrates can become deadly and begin affecting your fish past concentrations of 40 ppm. Generally, you will control nitrate levels via weekly water changes, diluting the chemicals and balancing the guppies’ environment.

When that doesn’t happen, adding a bit of salt can keep your fish safe. The chloride ions will form a natural barrier around the fish’s skin, preventing the excessive absorption of nitrates.

How Much Salt Can You Use Per Gallon?

The opinions vary on this topic since the answer depends on many factors. These include the type of fish, whether the water is fresh or marine, etc. As a general recommendation, you should use around 1 teaspoon of salt for every 5 gallons of water, but this isn’t a universal rule. The amount of salt to use depends whether you’re just stabilizing your guppies’ environment or treating them of fungal or bacterial infections.

I recommend discussing with a fish expert about your specific case to get personalized advice.

Do Guppies Like Brackish Water?

Yes, guppies like brackish water since this is their natural environment. Guppies can also adapt to marine and freshwater in case you’re looking to try out different things. Just make sure you gradually increase or decrease the water’s salinity so that your guppies won’t experience osmotic stress or shock.

Abrupt or vast changes in water salinity or pH can kill them.

Can You Use Salt for Baby Guppies?

I wouldn’t recommend it except if your guppy species comes from environments higher in salt. Even so, you may want to double-check whether it’s safe to do so or not. I only recommend using salt for your guppy fry in case of a bacterial or parasitic outbreak.

Or if your guppy fry show signs of osmotic shock, although that’s difficult to detect in baby guppies. To be sure, discuss the salt aspect with a fish professional for competent advice on your specific situation.

Can You Use Salt in a Planted Tank?

No, you can’t use salt in planted tanks. Be very careful where you’re sourcing your information since there’s a lot of erroneous advice out there. Especially on various fish-oriented forums. Salt pretty much acts as poison for many aquarium plants, especially freshwater ones.

Increasing the water’s salt content will cause the plant’s cells to shrink and die off, making the photosynthesis process impossible. This stands true for most plant species with notable exceptions. Seaweed is one of them. This species produces a specific thick coating, protecting it from taking in too much salt.

This is the main reason why hospital tanks are necessary when treating sick fish. It’s because the treatment may sometimes require medication and salt, both of which can kill plants and disrupt the main tank’s biofilm.


As an end note, I recommend speaking to a fish specialist about your guppies’ salt requirements. Take my advice on this topic with a, well, teaspoon of salt.

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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