How To Stop Water Evaporation In My Aquarium? : Causes And Remedies

Who doesn’t love to keep pets at home? And if you’re allergic to furry pets like me, then the aquarium pets are the perfect comforting companions for you. Some of you might already have water buddies at your home. As an aquarist, you may find troubles of water evaporation in your aquarium. However, aquarium fishes do have many health benefits.

Don’t you think they are therapeutic? Of course, they are. However, with every adorable pet comes great responsibility. You’re here to understand that, aren’t you? Great! Just know that these vibrant species are easy to keep but, they can be equally challenging sometimes, especially if you’re new to this fish-keeping hobby.

One of the common concerns is the aquarium water evaporation. You’ve clicked the right article for all that you need to know about how you can keep aquarium water from evaporating.

There isn’t a complicated science for your water evaporation from your fish tank. Liquid to gas phase transitions is known as “vaporization.” Similarly, your fish tank’s water evaporates when the temperature of your water increases. You don’t need to worry about aquarium water evaporating as its a natural phenomenon. However, if the temperature of the place you live in is way too high, you will have to use an aquarium chiller to cool down the heat of the aquarium to the temperature as the fish requires. Else you can just top off the evaporated water with freshwater to maintain the water level of the tank.

What is Aquarium Water Evaporation?

Aquarium Water Evaporation. It sounds familiar, doesn’t it? It seems like all that learning about ‘evaporation’ in our school days didn’t go in vain. The definition has finally come into use now. Evaporation is a process of liquid changing to gas or vapor. Oh! The nostalgia hit me hard. Anyways, my point is evaporation occurs in your aquarium, and it is a natural part of the cycle.

You might have noticed your aquarium water declining from the amount you’ve filled. If there’s a slight change in the level of water, it’s okay. But, if there’s rapid aquarium water evaporation, then it’s a matter of concern.

Why Does Aquarium Water Evaporate?

You already know, any heat source causes the aquarium water to evaporate just like in nature’s water cycle. You might be wondering why the aquarium water evaporates when it’s not even placed in the direct sunlight. You’ll notice a tiny bit of aquarium water evaporation anyway despite a great setup, and the sunlight isn’t the only cause of it. Several other factors build up heat in your aquarium, thus leading to evaporation. It could be dry air, room temperature, humidity, hot weather, tank heater, and even lightings.

Regular Aquarium Water Evaporation Rate

The aquarium water evaporation in a small amount is pretty decent. Your fish will do fine in it. Let’s say you have a 10-gallon aquarium. The average aquarium water evaporation rate for this aquarium is 0.18 gallons or half a liter per day. It’s relatively easy to calculate the rate of evaporation in your aquarium.

Calculate Water Evaporation Rate in Your Aquarium

Pour the ideal amount of water in your aquarium and trace the waterline on the outside of your aquarium. Measure the distance between the traced and the current waterline with a tape measure after a week. All you have to do is multiply the length and breadth of your aquarium with the measured waterline distance. The calculated outcome is the milliliters of evaporated water within a week. To calculate the aquarium water evaporation rate per day, just divide the result by 7.

Related article: Concept of aquarium size and weight

Causes of Rapid Aquarium Water Evaporation

As I mentioned earlier, if you see a boatload of evaporation in your aquarium, then it’s a matter of concern. Normal aquarium water evaporation is a natural process, but when it becomes rapid, you must keep an eye on the factors that might be causing it.

Open Aquarium

An aquarium without a lid is prone to a more significant amount of water loss in comparison to a close aquarium. If you have an open aquarium, it is already warming up with the filter and lightings. Furthermore, your open aquarium is in direct contact with the outer surrounding so, this will double-up the evaporation rate.


Your surrounding is the primary cause of rapid aquarium water evaporation. If the air is too dry or the room temperature is high, or the weather is too hot, there’s a high chance of rapid aquarium water evaporation.

Using a Skimmer

The use of a skimmer in your aquarium can speed up water evaporation. Running the skimmer all the time can drop the water level of your aquarium firmly. Unlike marine water aquariums, skimmers don’t work very well in freshwater aquariums. So, ask yourself whether you need a skimmer for your aquarium first before using it.

Using The Same Old Water Filter

The aquarium water filter purifies the water for your fish by collecting all the residues, leftover foods, and feces that sink into the substrate. If you don’t clean it regularly or change it frequently, then the filter gets clogged. And you know how hot old electronics get while functioning when they have malfunctioned. The clogged filter works without a doubt, but it heats the water of the aquarium leading to rapid evaporation.

Strongly Moving Water Surface

A good water movement ensures that your fish have sufficient oxygen. However, if it’s over the top, then this can be one of the causes of rapid water evaporation in your aquarium. Plus, this will stress out your water babies.

Lights On 24/7

Do you keep the aquarium light on all day and night? Well, well, well. The cause of rapid water evaporation is right here. When you keep the light on for the longer duration, it heats the aquarium water, thus leading to more evaporation.

Is Aquarium Water Evaporation A Big Deal?

YES. If you stay unbothered for a long time, then the aquarium water evaporation can be dangerous for your beloved fish. Don’t assume that all dissolved substances will evaporate along with the aquarium water. Only the pure water will evaporate, leaving the residues behind. The residue will harden the water and lower the quality of water. It makes it difficult for your fish to survive.

Rapid Aquarium Water Evaporation Is A Threat to Your Fish

Rapid aquarium water evaporation is even more hazardous for your fish. Since only the pure H 2O gets evaporated rapidly, all that’s left in the aquarium would be the dissolved toxins. The salinity and density of water increase in the marine water aquarium. Ultimately, the water quality declines to its lowest in the freshwater aquarium. It will affect the osmoregulatory system of your water babies leading to stress and diseases. Overall, the lives of your fish will be a living hell.

You don’t want this to happen, do you? You want to prevent this, but as a novice aquarist, you don’t know how to. Don’t worry. Keep on reading this article to find some handy ways to prevent aquarium water evaporation. But first, observe the signs of the rapid aquarium water evaporation.

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Signs That Aquarium Water Evaporation Is Getting Out Of Hand

Let me quote once again. “A small amount of evaporation is totally fine.” You can do the above calculation to find out if the water evaporation rate is average. But, if the water evaporating per day is on an extreme level, know that it’s getting out of hand.

Red Sticker

Many aquariums come with a little color spectrum sticker, ranging from green at the top to yellow in the middle and red at the bottom. When the waterline of your aquarium reaches to the green range, it means the evaporation rate is reasonable for your fish. The waterline at the color yellow is like a warning for you to top off or make some necessary changes. The waterline at the color red means you have to either change the water or find some other solutions to control it.

This sticker helps you to figure out that the evaporation is happening gradually. The step by step evaporation that shows the water declining from green to yellow to red is a sign that everything is fine. However, in some aquariums, water evaporates so quickly that the waterline reaches directly to the color red in a day or two. If it is also happening in your fish tank, know that there’s something wrong with the setup. This probably means the evaporation rate has gotten out of hand, and you’ll have to control it before things get worse.

Lack of Appetite

Fish lose appetite, usually because of diseases and infections. So, you might get confused about whether your fish lacks the desire to eat due to diseases or rapid water evaporation. Just observe the color spectrum sticker for a few days. If your aquarium waterline is falling rapidly to the color red in only a day or two and your fish is refusing to eat at the same time, then it’s a sign that your fish is getting affected by rapid water evaporation.

Related article: How to feed aquarium fish?

Gasping At the Surface

You’ll find your fish gasping at the surface while the aquarium water is evaporating rapidly. It might look like they are asking for food. But, the real reason is that the toxins and hardness of water lower the oxygen level in the aquarium. Your fish is gasping for air.

Loss of Color

When your fish is losing appetite and don’t have enough oxygen to breathe, this will affect not only their inner organs but the outer appearance as well. The first thing you’ll notice is the loss of color in your fish. All the shine of your fish fades away with rapid water evaporation.

Handy Tips To Prevent Aquarium Water Evaporation

Now, you might want to prevent the situation before it happens. To make it easy for you, I’ve listed out some tips below to stop aquarium water evaporation.

See The Signs

Is your aquarium waterline falling at the red-colored spectrum at once? Are your fish refusing to eat food? Or are they gasping at the surface? Observe whether the condition of your aquarium water and fish matches with all the signs of rapid water evaporation that I’ve mentioned above. If it does, then get ready to stop the water evaporation from increasing.

Take a Temperature of Aquarium Water

How can you set the right temperature of the aquarium water if you don’t have a good old thermometer? If you can, buy a digital thermometer to get an accurate temperature of the water. Check the temperature frequently. Turn down your tank heater accordingly to manage the relevant temperature range for your fish.

Change Your Water Filter

By any chance, if your fish touch the old clogged water filter, they will get severe burns on their tender bodies. Think about it. Seeing your darling fish in pain will hurt you. It will hurt you more if you can’t do anything about it. Before it happens, change your filter even if it’s a little time consuming for the sake of your fish’s well-being. Don’t forget to acclimate your fish after changing the water filter.

You Need a Lid For Your Aquarium

You might be keeping the lid off of the aquarium to give your fish a little pat on their head whenever you go near them. I can understand. But, you’re also making way for the evaporated water to get out by not putting a lid in your aquarium. Put the aquarium caps on to prevent the aquarium water from escaping. The water will evaporate no matter what, but the good thing is it will hit the lid and drop back into the aquarium.

Turn The Lights Down Low

There’s no need to keep the lights on at night. Shut the lights off of the aquarium when you go to bed. You’ll do two things at once. One, you’ll save electricity. Two, you’ll let your fish rest throughout the night. It will also reduce the growth of algae.

If you have fixed lights in your aquarium that gets hot quickly, you can do some research and opt for the best wattage light.

Turn Down The Heat

You might have researched the temperature requirement for your fish species before buying. If you see rapid water evaporation in your aquarium, turn down the heat slightly lower than the actual temperature.

Change The Aquarium Location

Shift the aquarium from the places that are comparatively hotter at your home. If your aquarium is in the kitchen, move it. I know you enjoy gazing at beauty while cooking, but the kitchen has a high temperature most of the time. Choose an area away from the direct sunlight, windows, heaters, and any other heat sources.

How To Compensate for Aquarium Water Evaporation?

You’ve learned about the ways to prevent aquarium water evaporation. In case the aquarium water evaporates, is there any way that you can compensate for the lost water and restore the initial conditions? Well, you can replace evaporate water in three ways. Here’s how you do it.

Topping Off

Now, as a remedy for evaporation, you might think of topping off your aquarium when the water evaporates. With proper preparations, you can refill your aquarium. Store the demineralized water at room temperature for a few days before refilling the evaporated water manually to the desired level. Remember to be very careful while pouring water as this might irritate your fish.

It can be a great solution until you find another solution within the next few days. While topping off can ease this problem for some days, you’ll have to make preparations to perform another method.

Semi-Automated with a Dosing Pump

This method is easy for novice aquarists. You just need to have a dosing pump. Before using this device, calculate how much water evaporates daily in your aquarium. Then, you can set the control unit of the dosing pump to refill the required amount of water. Since your fish might get irritated or stresses while changing water, divide the addition of water into small fractions. The dosing pump will then add the water in a small amount frequently per day.

Make sure that the water you use for refilling your aquarium is demineralized. And, the water reservoir connected with the dosing pump is large enough to fill water for a week. The evaporation rate is not uniform. So, you’ll have to monitor and adjust the dosing pump accordingly to prevent the aquarium water from overflowing.

Semi-Automated with a Sealed Box

It is an old-fashioned method that relies on atmospheric pressure to fill the evaporated water in your aquarium. You need to keep a sealed acrylic or glass box filled with demineralized above the surface of the aquarium water. A pipe connects the bottom of the box with the surface of the aquarium water. It is the only way for the demineralized water to fall from the box into the fish tank. The water from the sealed box fills the aquarium every time its water gets evaporated. At other times, the water will not escape from the closed box due to atmospheric pressure.

Fully Automated

Last but not least, you can purchase a fully automatic refill system. You don’t have to do anything here. Just sit and watch how it works. This device automatically refills your aquarium with the desired level of water with the help of sensors. The sensors sense the water drop in your aquarium and fill it with the help of a dosing pump. The dosing pump is connected to a water reservoir.

How To Properly Acclimate Your Fish?

If you remember, I had recommended acclimating your fish after changing the water filter. Here’s the tutorial for you to do it the right way. Acclimation is necessary when you shift your fish to your aquarium or when you do water changes. After all, your fish need to get used to your aquarium.

Acclimation doesn’t mean that you can let the bag float in your aquarium for a few minutes, and you’re done. That’s just the beginning. After allowing the bag float for about 15 minutes, cut a slit under the seal of the bag and pour 1/2 cup of aquarium water in it. Repeat this process after 15 minutes. After another 15 minutes, net the fish out of the bag and put them in your aquarium. Never make a mistake of pouring the water from the bag into your aquarium as it contains parasites.

Frequently Asked Questions

How Long Does Water Take To Dechlorinate?

It depends on the level of chlorine and the total volume of water because water can take 1-5 days to dechlorinate completely. No matter what, you must let the water sit for a minimum of 24 hours to dechlorinate.

Can Changing Water Kill Fish?

YES. Water changes are necessary because fish get stressed due to poor water conditions. However, too many water changes are also bad for fish. Fish need time to adjust to the aquarium, and they can’t handle extreme change. So, water changes in large volumes or lack of acclimation can kill your fish.

Also Read: How to clean and maintain tanks?

Do Fish Hide When They Are Dying?

Fish tend to hide when they are sick or stressed. They leave their food uneaten and remain inactive. When you notice your fish hiding, then quarantine it immediately and do the necessary treatments.

Does Ammonia Cause Water Evaporation From Aquarium?

NO. Ammonia doesn’t evaporate from the aquarium but would instead get dissolved in water. When the aquarium water evaporates, the dissolved ammonia remains behind, thus, contaminating the water. So, you need to perform at least 50% water change weekly, along with regular maintenance.

Keep the Aquarium Water Evaporation Away

As the proverb says, “Where there is a will, there is a way.” So, if you’re having trouble with the rapid aquarium evaporation, you can remarkably solve it. And there are plenty of ways lined up for you to do so. It’s in your hands. Always do some research before owning a pet. Never hesitate to ask for advice from the pet store owners.

Also Read: Easiest fish to breed

Related article: Health Benefits of Aquarium Fish

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