Why is my Fish Tank Water Evaporating?

Everyone that’s owned a fish tank and kept fish. Would have lost some water to evaporation some small loss is inevitable and perfectly fine. But left unattended over a short period of time can harm the fish and destroy the whole cycling of the tank!.

Why is my fish tank water evaporating?

Given there’s no leak it’s one of three things overheating overstocking or filtration issues! Check all equipment starting with the heater.

Main Reasons For Water Evaporation?

As said above there are a few reasons for Evaporation/water loss. Beginning with overheating caused by equipment mismanagement or failure. Ie Heater set too high or broken and staying on too long and or not turning off once heated to the desired temperature.

If there are signs of overheating and not any other issues then how to cool down your fish tank: Temp control! maybe of help!.

Or filter not being cleaned enough getting clogged or just not working correctly this can lead to overheating also the build-up of toxins.

Always check the heater and filter first making sure the equipment is working also checking the thermometer is working there’s no harm in having a few of those around.

After eliminating equipment failure or readjusting if set wrong we can look to the fish themselves to tell us more. If the tanks are overstocked they will generate more heat in the water and or less movement across the surface causing evaporation.

Also if fish are in water that’s too warm they tend to rapidly lose appetite.

Overheating fish may also lose colour and begin to gasp for air at the surface these are the main causes to look out for in water loss.

Is Evaporation Bad?

YES. If left untreated and evaporation continues for a long time, water loss can be dangerous for the health of the fish. Don’t assume that everything will evaporate along with the aquarium water.

Only the water will evaporate, leaving the residues behind. The residue will harden the water and lower its quality of water. It makes it difficult for your fish to survive.

While it might not seem a problem to lose some water it can be deadly to fish if you let it go for too long. As the water evaporates, it leaves behind the nitrate and ammonia particles that come from the fish’s poo. If the levels get too high, then the water becomes dangerous for them.

New fish owners might think  evaporation in their tank is “okay, well, let me just top it off.” Topping off means adding more water into the tank bringing the water levels back to where they were, to begin with.

While this is alright maybe once, continuing to top off your tank when you notice evaporation only leads to stronger ammonia and nitrate levels.

Topping off is a great idea if you’re in a pinch and are planning to fix the problem within the next 1 to 2 days. However, once you do so, you need to keep in mind that it is not a replacement for changing the water and changing your equipment to ensure everything is working properly.

Too Many Water Changes

That all being said, too many water changes are also bad for the fish, especially if they are not properly acclimated. Fish live in their tank and in their water, which creates a natural environment that allows them to thrive.

Changing the water strips the tank and the fish of that environment, which can stress them out even more than any nitrate and ammonia buildup.

When fish get stressed out, they will stop eating and die. Usually, you can tell when a fish is getting stressed as a result of poor water conditions. Because they’ll start gasping at the surface of their tank.

It will almost look like they’re begging for food, even if it isn’t their regular mealtime. They are begging for air, though, because there isn’t enough oxygen circulating in the tank.

Water changes are necessary, of course. Depending on how full your tank is, you should be changing anywhere from 10 to 30 per cent of the water each week. That way, you’re not stripping the tank bare, and you’re not simply adding water on top of the dirty water to compensate for evaporation. You should never go more than a month without a partial water change.

Signs Of Evaporation?

There are a few signs to look out for when it comes to water loss first is checking the temperature of the tank against a good thermometer making sure the tank is constantly at the desired level.

Secondly most if not all new aquariums come with coloured stickers on the side that tell you if the tanks losing or gaining heat!.

Thirdly you could or should draw a line on the tank when filling and acclimatizing the tank when first cycling.

This will give you a reading of the desired water level if it starts to drop below this line you will now know and can pay closer attention.

The final few signs are a bit more advanced in the later stages you would already have lost some water. But it’s still rectifiable the fish will have a loss of appetite seem sluggish maybe have a loss of colour and or becoming to the surface gasping looking for air.

How High Should Water Level Be?

Always use as much room as you can as a general rule of thumb filters need water level to be about one inch from the lip of the tank. 

You should generally fill the tank up to an inch below the trim because the water column and aeration system will create bubbles that splash the surface. When the waterline is too high, water may splash outside of the tank. Jumping behaviour isn’t unusual for fish.

Best to have a lid on your tanks to prevent jumping fish. Read more here on Do Fish Tanks Need A Lid?.

The lower you have the water line the more problems this creates as there’s less room for beneficial bacteria to grow and bad toxins can remain above the water where the filter cant reach!.

Make Sure It’s Evaporated And Not A Leak

Aquariums believe it or not leak due to the sealant in them starting to get worn out. The sealant is the layer of black substance that is responsible for keeping the glass panes of your aquarium glued together to create the shape of the tank.

Here’s a replacement sealant safe for aquarium use Aquarium sealant. 

This sealant over time can become worn out. As a result, your fish tank slowly starts to leak water without any noticeable cracks on it.

A common trick to finding the leaking spot in your aquarium is to wrap a paper towel around it. The paper towel will get wet on the spot where the water leaks from.

This way you will quickly find out exactly where the sealant is worn out and causing a leak. Furthermore, another useful trick to spot the leak in your aquarium is to notice where the level of water became constant.

Most small leaks that are pin-sized and or sealant damage can be fixed!

How To Stop Evaporating Water?

As we have discovered within this article some small loss of water is fine and common but if it’s more than a few inches we need to rectify it.

Thankfully this is easy the main thing is to fill and check for leaks before even using. Then once cycled and fish are in and acclimatized we need to keep a check every few days on the waterline and once a week check on the heater to make sure all is looking ok.

Obviously, we can check every day the thermometer to double-check also as stated previously having two thermometers on each end of the tank will help too. We can also check the filter every week or two the best time is on the routine water change doing these things along with not over deeding or overstocking the tank should alleviate any evaporation issues!.

How To Replace Evaporating Water?

Replacing lost water or Topping off as it is sometimes referred to can be done but not regularly as continually refilling can course stress to fish use room temp or warm tap safe reverse osmosis water and only if it’s a small amount of lost water an inch or two anymore and you may as well do a water change!.

Evaporation Tray?

Basically, a tray that is placed in the hood and or lid of the tank that catches water vapour and separates the vents and wires from other equipment. Keeping everything safe and letting you know how much water is being lost don’t reuse this water tho!.

Other Tips And Things To Look Out For

We can’t completely eliminate evaporation. You can make changes, like decreasing surface agitation, most tanks need water movement, lighting, and filtration.

But there is a way to combat water loss!. If you’re having to add water every day, an automatic top-off (ATO) system is just what you need. The full system consists of a water level sensor, a water reservoir, and a small pump.

An ATO automatically senses when the water level in your tank or sump is too low. The ATO turns on the pump, adding RO water back to the aquarium.

The sensor switches the pump off once the correct water level is reached. ATO are safe and reliable. They even have safety sensors that prevent over-filling. An ATO eliminates the need to add water every day. Just keep the reservoir full and the ATO does the rest.