Water Type for Guppies – 5 Options to Consider

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Having a thriving guppy tank involves considering various aspects, including guppy-to-water-gallon ratio, diet, water temperature, parameters, etc. Which water type to use for the tank is also a critical aspect that many people will ignore.

This is a potentially costly mistake since using fluctuating water parameters could kill your guppies. Not to mention, some types of water are straight-up unfit for your guppies and other fish.

But how many types of water do people use, and what problems can they face as a result? Let’s see if we can shine some light on the matter.

Is Tap Water Safe for Guppy Fish?

No, it isn’t. This isn’t probably the answer you were expecting since tap water is safe for humans, so that would mean it’s safe for guppies as well, right? Well, wrong. Tap water contains chlorine which is used to sterilize it and kill off harmful bacteria and dangerous agents.

In other words, the addition of chlorine makes tap water safe for human consumption. Unfortunately, the same chemical can prove deadly to aquarium fish, depending on its concentration. Fortunately, the chlorine will evaporate from the water rather quickly, especially if you intervene to speed up the process.

There are 4 common ways to dechlorinate tap water to make it safe for your guppies:

  1. UV Exposure – This is pretty much self-explanatory. You only need to collect the tap water in an open container and expose it to direct sunlight. You may need 24 hours at least to achieve the desired effect. It takes time, but it works so long as this is the only option you have.
  2. Boiling the water – The boiling process alone is enough to degas the water and evaporate the chlorine forcibly. Water chlorine evaporates on its own under normal conditions; boiling the water only speeds up the process.
  3. Using vitamin C – I bet you didn’t see this one coming. Vitamin C is actually quite a potent dechlorinator that also removes chloramine. The downsides include requiring around 40 mg of vitamin C per gallon of water and an increase in water pH levels.
  4. Using a professional dechlorinator – This is a commercial solution specifically devised to assist with water dichlorination. Some professional dechlorinating solutions also combat ammonia and nitrates, providing multiple benefits for the same price. It’s probably the best option for dechlorinating the water and providing your guppies with a safe and clean environment fast.

Can You Use Spring Water for the Guppy Tank?

Yes, but the truth isn’t as simple as you might think. People tend to associate spring water with fresh, clean, and healthy, but that’s hardly the case anymore. If we’re talking about natural spring water, never presume that it’s safe for your guppies simply because it’s natural.

Springwater may contain a variety of contaminants, especially when near cities and pollution sources like factories. Before reaching you, you have no idea where the spring water comes from or what it has collected from the ground or air.

I advise getting commercially-sold spring water, although that’s not without some minor controversy either. Commercial spring water can vary in price wildly depending on the manufacturer and can contain various minerals in different quantities. Finding the one that best suits your needs requires some basic research before purchase.

Other than that, spring water is excellent for stabilizing the tank’s pH levels and providing your fish with essential minerals. Just make sure you get it from trustworthy sources.

Is Distilled Water Good for Guppies?

No, it isn’t. Distilled water is practically sterile in terms of mineral content. It contains no magnesium, iron, calcium, or other mineral that your fish need to remain healthy and thrive in their environment. These minerals nourish the fish and ensure the healthy functioning of the fish’s nervous system via their ion content.

The same minerals will also stabilize the tank water’s pH levels, which becomes impossible if you rely on distilled water.

All this means that you shouldn’t use distilled water for your guppy tank, not even for water changes. You can only use it to replace evaporated water (which happens in time and in small quantities only), which doesn’t deprive the tank water of any minerals.

After mineralization, you can also use it, which is nothing more than enriching distilled water with the essential minerals that your guppies need.

Is Well Water Safe for Guppy Fish?

I wouldn’t recommend using well water for your guppy tank for 2 main reasons:

  1. The high risk of contaminants – Well water isn’t regulated, which means there’s no way of knowing whether the water is clean of dangerous bacteria or contaminants. The problem here is rather obvious. You also have no way of knowing how to treat the water since you don’t know what it contains.
  2. Low levels of oxygen – Well water also has low oxygen levels, requiring you to aerate it before use. This alone sounds like too much trouble when there are so many better options out there.

Can You Use Rain Water in a Guppy Tank?

I would advise against it. Like well water, rainwater will come with many variables, making it unsafe for your guppy tank. There are several core problems with rainwater that make it unfit for guppies:

  • Varying pH, placing your fish’s health at risk
  • Low mineral content that will affect your fish directly
  • An unknown quantity of contaminants and pollutants, many of which could prove deadly to guppies

The problem with rainwater is that it doesn’t really matter where you live. You could be living in a rural area with low-to-no high-profile sources of pollution around, and it would make little difference. Air pollutants disperse into the air and can travel for hundreds or thousands of miles until being mixed into the rainwater that will pour over your home.

Just like with well water and other unregulated water sources, there’s no way for you to control the water’s content or ensure it’s safe for your fish.

Best Water Parameters for Guppies

Guppies are adaptable and resilient fish that thrive in balanced and stable environments. They like tropical temperatures, flowing water, and a plant-rich habitat to provide them with hiding places and occasional snacks.

That being said, guppies can adapt to some changes in their habitat’s parameters, but not too abrupt. If you want to keep your guppies healthy and thriving over the years, I recommend providing them with a stable environment, preferably packing ideal living conditions. 

The best water parameters for guppies include:

  • Temperature – 72 to 82 °F. Wild temperature variations with cause guppies several problems. Excessively cold waters will destroy the fish’s immune system and make it prone to infections, diseases, and parasites. Excessively warm waters will have critically low oxygen levels, with your guppies risking suffocation as a result.
  • Water pH – 6.8 to 7.8. Extreme variations in the pH level can stress out guppies, lowering their immune system and making them more prone to illness. An extremely low pH will also turn the water acidic, which can kill your fish directly. You can change the water’s pH levels to ensure the stability of the habitat. If the pH is too low, add 1 tsp. of baking soda to 10 gallons of water. If the pH is too high, you can use a carbon dioxide injector to lower it. However, the water’s pH will remain stable if you change the water regularly and have a flourishing aquatic flora.
  • Water Hardness – 8 to 12. The key aspect to remember here is a direct correlation between water hardness and pH levels. In other words, when one value increases, the other will follow. You can control water hardness by performing regular water changes, keeping the guppies’ habitat clean and healthy. I recommend changing between 10 and 20% of the water every 5-7 days.

Aside from these parameters, you should also monitor the water ammonia, nitrates, and nitrites. You should have 0 ppm ammonia, 0 ppm nitrites, and 10 ppm nitrates at most.

Changing Fish Tank Water for Guppies

The process of changing the water isn’t difficult, and it won’t take too much of your time. Here’s what to consider when changing your guppies’ water:

  • You must perform regular water changes – This is an important aspect, especially since many guppy owners minimize its importance. I’ve seen people claiming they haven’t changed their guppies’ water for months or even never. Your guppies will adapt to some level of dirty water, but with a limit. Unclean tank water can become murky and cloudy and harbor high levels of ammonia and nitrites. These can prove lethal for your guppies with time. The oxygen levels will also drop in dirty waters, which comes with a variety of specific issues.
  • Control how much water you change – You don’t want to change too much water at once, thinking you will save time by performing fewer changes. Massive water changes will disrupt the tank water’s biofilm, depriving guppies of essential minerals and beneficial bacteria.
  • Prevent major temperature fluctuations – Don’t disrupt the tank water’s temperature since it will affect your guppies. Guppies can withstand rather impressive temperature variations, but not sudden ones.
  • Use a conditioner – A water conditioner will cleanse the water of heavy metals, ammonia, nitrites and remove the chlorine if you’re using tap water. Get a good, reliable product and keep your guppies safe.


The water you’re using for your guppy tank can make or break your guppy population. The tank water is their living environment, just like the atmosphere is for land creatures.

I suggest using tap water for your regular water changes, but always in small amounts (10-20% of the tank water volume) and always after removing chlorine. Use a water conditioner, perform regular water changes, and provide your guppies with optimal water parameters, and your guppies will thank you for your care.

Updated: June 14, 2022
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