How to Change Water for Guppies?

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If you’re a guppy keeper, you probably already know that regular water changes are vital for your guppies’ wellbeing. Regular water changes improve oxygenation, inhibit the development of harmful bacteria, and keep guppies’ habitat clean and fresh.

But if you’re new to the scene, how should you perform a thorough water change?

Today’s article aims to explain how to change your guppies’ water step by step to avoid any mishaps. Here’s what you should do.

Changing Aquarium Water for Guppies

First, you should know that the typical aquarium will host a variety of bacterial cultures. Some are harmful, while others are beneficial. The later ones will generally consume the ammonia and nitrates that result from fish waste, decaying food, and dead fish and plants. In other words, they will keep the tank clean, contributing to a healthier and more stable ecosystem.

These beneficial cultures will spread throughout the tank, and you can even find them in the filter. For this reason, sterilizing the tank’s equipment is never a good idea since it will kill off the beneficial bacteria.

With that in mind, here are the key steps to follow when changing the tank’s water:

– Disconnect the Aquarium Equipment

Many people will skip this step, which is a mistake. Changing the tank’s water involves a lot of maneuvering around the tank, usually while carrying buckets of water. All this activity can damage the tank’s equipment in the process. Not to mention, it’s never a smart move to play with water near electricity.

Unplug everything with care and move the equipment somewhere safe. This includes the lighting and heating equipment, filter, and whatever else you might have installed, depending on the setting.

– Drain the Water

Once you’ve removed all the equipment, it’s now time to drain the quantity of water necessary for the job. This depends on your tank’s size. You only need to change 15% to 20% of the water for small tanks, while larger ones may require 30% to 50% water changes.

This also varies depending on how many fish you have. If you have more than 1 guppy per 2 gallons of water, you may need to perform more extensive water changes to prevent the water from going foul.

This step involves draining the amount of water necessary and cleaning the gravel at the same time. One useful tool to help you at the job is the Laifoo Aquarium Siphon Vacuum Cleaner. This is a durable and effective vacuum with a 5-feet hose and made out of durable components. It is excellent at cleaning the gravel and sucking the water without disturbing the fish in the process.

Such a tool is ideal for the job since it maximizes efficiency and minimizes the time spent during the clean-up process.

– Prepare Fresh Water

If you’re using tap water, which most guppy keepers do, you need a water conditioner. The water conditioner is useful for neutralizing all chemicals that are usually present in the tap water. These include substances like chlorine and other chloramines that are harmless to humans but might kill guppies and other fish.

You should also stabilize the water’s temperature parameters before adding it to the tank. For better results, I advise monitoring the temperature in both the main tank and the recipient holding the new water. For guppies, you should aim for values between 72 and 82 F.

Slight variations in the water’s temperature won’t hurt your guppies so long as they’re not too drastic. Once the temperatures equalize, the water is now ready.

– Pour the Water

While this action seems simple enough, reality is quite different. You can’t pour the water into the tank however you like; you need a minimum of finesse and consideration for the environment. So different that I felt obligated to write a subtitle focusing on this precise aspect.

Pouring the water too fast may disturb the tank’s decorations, ruffle the gravel, and even damage the plants and fish. To prevent such unfortunate scenarios, I suggest gradually moving the water into the main tank using a smaller recipient. You can even pour it straight from the bucket with care, so long as it doesn’t affect the tank life.

– Reconnect the Aquarium Equipment

After you’ve changed the water, you can now reconnect the tank’s equipment as it used to be. Tread carefully not to disturb the fish in the process.

You should also be careful around the electrically-powered equipment. Always handle them with dry hands to prevent any accidents.

After the water change is complete, make a note in the calendar. Keeping track of the procedure will allow you to create a stable schedule, as you need to perform weekly water changes.

How Often to Change Water for Guppies?

The frequency by which you need to change the water for your guppies varies based on a variety of factors. These include the tank’s size and how many fish you have. A small tank will require more frequent changes and more water being changed during each session. The same goes for overcrowded tanks with multiple fish species.

These environments will create the most waste, fouling the water faster than larger tanks with a balanced guppy-per-water-gallon ratio.

Typically, you should perform weekly water changes, each time changing around 10% to 20% of the water. In some cases, the amount of water needing change may increase dramatically. Such is the case with hospital tanks, where you treat sick guppies and use antibiotics and other medication.

In these situations, it’s necessary to change 50% to 70% of the water.

Is Tap Water Good for Guppies?

Yes, tap water is good for guppies, as long as you treat it before adding the fish. You need to realize that guppies are freshwater fish and freshwater isn’t the same as tap water. Although many people fail to make this distinction.

Tap water contains a variety of chemicals like lead, chlorine, chloramines, mercury, and other substances that will hurt your fish. Chlorine, especially, can kill them since it can be found in high quantities in tap water.

As I’ve already shown, a conditioner is necessary to cleanse the water of all these compounds and make it safer for guppies. You have endless products available on the market, each with its own specifics and effects. I suggest relying on one with multiple positive reviews.

Can You Use Rain Water for Guppies?

It’s rather difficult to answer this question since there are several variables to consider here. Rainwater is technically better than tap water simply because it doesn’t contain chlorine. It’s also obvious that wild guppies get their fair share of rainwater since tropical areas are warm and humid environments.

The problem that arises is that of pollution. Rainwater is nowhere near as affected by pollution compared to that in urban areas. Rainwater may contain chemicals that will hurt your fish in the long run. That’s why I don’t recommend keeping your guppies in an outside pond if you live in a heavily populated city.

Not to mention, rainwater is also poor in minerals and comes with a varying pH level. You definitely need to treat it before adding it to the tank. With that being said, you can use rainwater for your guppy tank, so long as you’re thorough about it.

You also shouldn’t rely on rainwater too often, precisely because it comes with so many variables.


Water changes are vital for all tank life since they clean the environment and improve the habitat’s oxygenation. You only need to perform one water change every week so long as the tank is not overpopulated.

Follow these article’s instructions and comment below if you still have questions about the procedure.

Updated: November 16, 2021
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