How To Treat Smelly Aquarium Water


How to treat smelly aquarium water? Maintaining fish tanks is fun as you see another ecosystem bloom under your care. However, a stinky aquarium could be a problem. Generally, fish tanks only have a mild and pleasant scent. Clean freshwater tanks, for that matter, have an earthy aroma comparable to freshly tilled soil. But it is only a soft scent that you could only smell when you are near the aquarium.

If your tank emits a strong, musty smell that you could sniff across the room, it is time to do some cleaning and maintenance. This guide will teach you how to treat smelly aquarium water.

Why Does Your Fish Tank Stink?

Before going over how to remove the stinky smell from your tank, it is best to know their common causes. Bad smells in fish tanks are usually caused by decaying biological materials such as rotting fish, decomposing plants, or excessive amounts of food in the water.

Dead Fish

As unfortunate as it is, the most common reason for a smelly tank is a dead fish. If your aquarium is too crowded with decoration and plants, it is harder to spot that a fish is missing or has died. It may even take you days before you realize that something is wrong. Usually, it is the rotting smell that will give it away.

A rotting fish releases sulfur and ammonia compounds, which creates a strong smelly odor. Locating the remains and removing them from your tank should take care of the foul smell.


Overfeeding is a common mistake among tank owners, especially the begginers. You should watch the amount of food that you give to your fish friends. The excess food that your fish does not consume ends up falling and accumulating at the bottom of the tank. The food build-up will start to decompose and will begin to release a strong foul odor.

Fish Waste

Like any living organism, your fish also produces waste. Without regular maintenance, these fish wastes could accumulate and will stink. An overstocked tank could also be a problem. When too many fish lives in your tank, the more fish wastes there are. But if you carry out cleaning and maintenance regularly, then this should not be a problem.

Decaying Plants

Aquarium plants help build a healthier and beautiful tank. However, when these plants die and decompose, they could make the whole tank smell bad. Dead plants turn to a black or brown color, so they are easy to identify. Removing the decomposing plants will eliminate the odor.

Clogged Filters

Your filtration system is responsible for removing wastes and debris from your water to ensure a clean and healthy aquarium. With a clogged filter, the rubbish in your tank could accumulate, releasing foul odors.

How to Treat Smelly Aquarium Water?

The first thing you must do to get rid of the foul smell from your tank is to identify the foul odor’s source and remove it. Start by taking the inventory of your fish. Check if any of your fish friends are missing. If there is, you need to locate its remains. Check for every corner, plant, decorations, and nooks in your tank where the body might be. Once you found it, promptly remove it.

Meanwhile, if your fishes are all alive, check for any decomposing plants in your tank. It is quick to spot decaying plant matter as they turn into a slimy brown and black color. Remove the decaying plant and make sure nothing is left of it on the tank. Also, trim any leaves that are dying.

If it still isn’t the plants, it might be due to wastes build-up. Check the bottom of your tank. Check every tank decoration and any hidden corners where uneaten food or fish poops might have accumulated. Make sure that your water filter is working correctly. After identifying the stink source and removing it, thoroughly clean the whole tank and change the water. Do a smell test to make sure that the odor is completely gone.

How to Preventative Smelly Aquarium Water?

Now that your tank smells excellent again, here are ways to keep your aquarium clean and odor-free.

Regular Maintenance

Proper and regular cleaning is vital to keep your tank smelling good. The purpose is to eliminate any wastes and debris that may be present in your aquarium. Not only does this prevent any foul odor from developing, but it also ensures a safe and clean environment for your fish. Take some time to clean your tank by doing the following:

  • Prune dead plants
  • Clean the bottom of the tank
  • Wipe the aquarium glass
  • Clean any tank decorations
  • Clean the water filter

If you refuse to clean your tank for a long time, wastes will only accumulate, and the smell will worsen over time. Keeping and sticking to a cleaning schedule is what a responsible tank owner should do.

Regular Water Change

After eliminating the source of the smell from your tank, it is best if you keep changing at least 10 to 15 percent of water from your tank over the next few days to get rid of any bad smells completely.

Carbon Filter

Adding a carbon filter is an effective way of eliminating any odor-causing molecules from your tank. Activated carbon absorbs foul smells and stops them early on. However, the filter needs replacement regularly to continue working.


As you might have noticed, the real reason for a smelly aquarium boils down to poor tank maintenance. The sources of all the foul odors are from rotting matters in your aquarium. If you clean your tank regularly, you should be able to find any rotting dead fish or decaying wastes in the water quickly. You can get rid of them even before they start smelling so bad then you don’t have to suffer from the stench of your tank.

A stinky aquarium is unpleasant to have. But now you know how to treat smelly aquarium water and its proper maintenance, it shouldn’t be a problem again.

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