Why an aquarium water change is important and how to do it

The Scottish poet Charles Mackay once said, “Water is the mother of the vine, the nurse and fountain of fecundity, the adorner, and refresher of the world.” Ok, so maybe a little over the top, it’s probably easier to remember the quote from Zoolander, “Moisture is the essence of wetness, and wetness is the essence of beauty,” and if you want to be reminded of that fabled scene, Check out the video below.

So what are we getting at? Water is the thing your fish live, eat and play in; therefore, it is essential to their welfare and happiness. This article will explore why aquarium water changes are important as well as explaining how to do one. 

Why is changing water important 

let’s tackle the elephant in the room, why do we need to do this in the first place, why is water changing important. We mention above that fish inhabit and live in water. Cast your mind back to your school days; imagine your classroom or student housing at University/College. You lived and worked in those environments, usually with other people. What would happen if no one tidied or cleaned in those areas…mess, dirt, and food would all build-up, causing the area to smell and look dirty/untidy and possibly over time leading it to become uninhabitable. 

This principle can be carried into fish tanks, you have to keep the communal living area for fish clean and healthy, and the critical way in doing this involves partial water changes. However, recently, since the introduction of filtration systems, and chemical filter media, most people often overlook its importance. However, with or without the filtration systems, water changes are essential!

So if we boil down and distill the above, aquarium water changes are paramount to the success of every fish keeper’s journey. Not only does it help improve the clarity of the water, by eliminating the discoloration and odors inside the aquarium. The clear water also helps to support the health of the aquarium creatures. Constant water changes will keep the conditions within the aquarium tolerant for the fish and other organisms.

Ok, so scientifically why are they important, what is it doing? 

Point 1: 

Cast your mind back to your chemistry and biology classes, probably when you were between the ages of 13 – 16. Fish tank water hosts a load of organic wastes. The wastes tend to break down and release nitrogenous products, phosphates, and other chemical elements in the water. These elements affect the water quality and create an acidic environment within the aquarium by changing the PH levels. 

PH stands for power of hydrogen or potential for hydrogen and is a scale from 1 to 14 that measures how acidic a water-based solution is. 1 is highly acidic, think of Hydrochloric Acid, and 14 is an Alkaline, think of bleach. 7 is neutral. Generally speaking, tap water should sit between a PH range 6.5 – 8.5, and this is the range we want to sit between when we think about our fish and their longevity. If you start getting close to 5 and below, your fish will begin to die, which is what we want to avoid like the plague. Aquatic life tends to do well in high and stable PH levels. Therefore, tampering with the PH levels in any way can result in dangerous conditions, especially in saltwater aquariums.

Point 2:

Aquariums also host lots of nitrogenous pollutants like ammonia, nitrite, and nitrate. These nitrogen compounds are harmful to the fish and other organisms within the aquarium. Through biological filtration, the ammonia is converted into nitrite then nitrate. High levels of nitrates will cause chronic stress to the fish, we have covered this before in our article here, however, you want to keep nitrate at or below 40 ppm (parts per million). If you don’t, the fish can become more prone to diseases and infections. In severe cases, the fish may end up dying. Excessive ammonia, nitrite, and nitrate can also result in the overgrowth of algae. Constant water changes help to keep everything just mentioned from happening.

Do I have to remove all the decorations and apparatus in the tank when I clean it?

No, which is great news! Partial water changes do not require you to take out the apparatus, decorations, and systems (filters, etc..) in the tank. This makes your life a hell of a lot easier, plus it does not stress your fish. How would you like it, if every time you cleaned/tidied your house you moved all the contents including the furniture outside, it would be a nightmare!

Should I take the fish out of the tank when the cleaning commences?

Again, another no. The fish will remain in the tank at all times, as you do a partial water change. Constantly moving fish in and out of a tank stresses them out, trust me, I know. This doesn’t mean you can neglect them entirely as you change the water, whether you use a bucket or a more sophisticated method such as a gravel vacuum, you will have to look out for the fish as you commence the partial water change.

How often should I change the water in the tank?

There is no definitive answer to this, the frequency varies and depends on the volume of fish, amount of food in the tank and the tank maturity. An established tank, you can wait much longer between water changes. Whereas if it’s a newer tank, you won’t have the beneficial bacteria built up. Meaning you’ll want to do water changes more frequently, depending on how the fish look in the tank. If the water is cloudy, chances are it’s the emergence of algae and you will want to change the water. 

It is considered safe for fish to live in a nitrate environment at 40 ppm (parts per million) or below. This is what you have to aim for in order for your fish to survive. Therefore, we need to monitor this by buying a testing Kit; we talk about this in our article ‘How to set up a Freshwater planted aquarium.’ There are conflicting views on how regularly you need to do a water change. However, numbers often bandied about by aquarium enthusiasts include a (25%) partial water change once week to a full water change every month. Again it all depends on how quickly you breach or reach 40 ppm; this is the critical factor in deciding the frequency of the water change. 

How do you carry out a water change?

Tip 1 – Don’t use a bucket or cup!! You might think I have gone mad; I haven’t. This approach is a pain, inefficient, and very messy. Even with a small to nano tank (2.5 gallons), we would advocate using our tip 2 method below. However, if you decide to use this old fashioned approach, make sure you use a bucket/cup which is only used for your tank. You hear horror stories of people using buckets that have been used to hold household detergents and liquids; this is something you can imagine you want to avoid at all costs.

Tip 2 – Ok, so what do we think is the best approach! What method supersedes the traditional above method. A Gravel Vacuum siphon is the best way to change the water in your tank. There is a system, it’s quick, and will mean no mess is left anywhere. This is what we advocate, and most tank owners of all sizes and experiences do and should use it. It will make your life easier and is the least obtrusive method for your fish.

Tip 3: Unplug the lighting and heating elements. It is essential to unplug these elements because you will be working with water around the tank. Everyone knows what happens when electricity comes into contact with water and you want to avoid this.

Tip 4: Disconnect the filters. It’s a good idea to disconnect and unplug the filters while changing the water. You can also clean it separately using a sponge.

Should the new water be heated 

Heating the water to the correct level is important, as you want to recreate the ideal temperature for the inhabitants in your tank. A simple way to do this, when filling up the tank again, make sure the tap which is responsible for feeding the bucket/ cup or gravel vacuum is heated to the correct temperature before the returning water goes back into the tank, you can measure this by using a thermometer.

What does treating water mean, is this necessary?

What are we talking about here, please explain? You can treat your water before it goes into the tank or after you have done a partial water change in the tank. Essentially you’re dechlorinating the water, making the chlorine and Chloramine in the water harmless for you fish and the other biological inhabitants, a posh way of saying plants. You can buy these online or at a store and they are very cheap to buy. You don’t have to do this, but most fish lovers do, as it allows you fish to live and play in conditions suitable for them to thrive and have fun. 


You hopefully now understand the what, how, and why about a partial water change. We have provided you with a clear structure and guidance on how this can be done, and we wish you all the best when you take on this challenge, although it’s a challenge, it is crucial and can’t be overlooked. If you have a different way or a different tip, please reach out and let us know.

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