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do pet fish smell bad

Do Pet Fish Smell Bad? Even If You Maintain The Aquarium Well?

Believe it or not fish are one of the most odorless pets that you could consider giving a home to. They do not like dogs and cats leave odors all over your house, and in general, are not considered a dirty animal.

This is not to say that fish do not smell at all, and nor does it mean that the answer to the question ‘do pet fish smell bad?’ is automatically no. Rather, it means that certain circumstances aside, which we will look into in a moment, pet fish are relatively non-smelly!

Do pet fish smell bad? Many factors will cause your aquarium to smell but fish themselves do not smell. Water conditions, maintenance, and rooting food are the main causes of smelly fish tanks. Fish are odourless creatures and do not have sweat glands and therfore do not sweat or smell.

What Do Pet Fish Smell Off?

Generally speaking, it is not actually your pet fish that smell at all! It is more the aquarium and water that they are housed in that carries an odor. For freshwater species, this aroma will be one with a tinge of freshly tilled soil, an earthy smell. For saltwater, it is more of an ocean scent, similar to that which you would smell on a beach.

It is worth noting that the room in which your fish are, both saltwater and freshwater, should not carry the odor of your aquarium. Rather, the smell of your aquarium should only be noticeable when you are stood in front of them with their lids removed. If your whole room does smell like your aquarium, then there is probably something wrong!

Why Does My Aquarium Smell Bad?

If your aquarium does smell bad, especially to the point where it is stinking out your room, then there is absolutely, 100% something wrong!  What this is will vary but no doubt it will be caused by one of the following seven things:

  • Overfeeding of fish
  • Too much fish poop
  • A dirty filter
  • Smelly water conditioner
  • Substrate problems
  • A dead fish
  • Plants rotting

Overfeeding Of Fish – Whilst we don’t want our pet fish to starve, we also need to avoid, at all costs, overfeeding them. This is not only due to food waste being a major cause of bad odors within an aquarium, but also because it can lead to health issues in your fish.

Regarding smell, fish will only eat so much food in one sitting, with the excess sinking to the bottom of their aquarium. This food which then sits on the bottom uneaten starts to break down releasing gasses which cause a foul odor.

As they say, prevention is always better than cure, so to stop this happening you should only feed your fish what they can eat within around five minutes. Read our article on this topic.

Too Much Fish Poop – Fish poop breaks down quickly in an aquarium and is often responsible for bad odors relating to them. This is especially true of aquariums that may be overstocked or contain heavy waste producing fish such as Goldfish.

Should you find you have a ‘too much poop’ odor emitting from your aquarium you should act quickly. Gravel vacuuming the substrate should remove most of the poop with the smell disappearing shortly after. We use the Python No Spill Vacuum Syphon which is amazing and easy to use. We found it on Chewy.com one of the largest online aquatic retailers.

Once again, however, prevention is better than cure and can be easily attained. Simply do not overstock your aquarium and keep maintenance regular. Please note there are some exceptions to the overstocking rule with Discus being one of them. For aquariums that are purposefully overstocked more regular maintenance is needed.

A Dirty Filter – Uneaten food, poop, and other things we have yet to mention, will be sucked into your filter whose job it is to remove dirt and debris from your aquarium. This can mean, that once trapped inside this mass of gunk, put simply, stinks!

There is no way, really, to prevent a certain level of odor emitting from your filter as it is designed to suck up the smelly and dirty waste. However, you can ensure regular cleaning of this important piece of equipment keeps this smell unnoticeable. Be sure to only rinse filter media during the cleaning process so as not to risk removing the good bacteria.

Smelly Water Conditioner – As strange as this possibly sounds a good deal of water conditioner brands have a distinctive and not always pleasant odor to them. This is, however, not a problem for most people who can tolerate this stench long enough for the water conditioner itself and the smell to dissipate within the water.

For those who can’t stand the odor, avoiding water conditioners with sulfur in will solve the problem. These are readily available in most aquatic stores and stop people not using a water conditioner at all because of this issue.

Substrate Problems – If the smell that is emitting from your aquarium resembles rotten eggs, it is highly likely that it is down to a rather complex problem with your substrate.

For the sake of simplicity, and time, basically your gravel or sand will compact over time producing areas where there is no oxygen. These areas in turn trap waste which bacteria turns into gases, very smelly gases! These then rise in your aquarium until the point they assault your nose!

You can, thank goodness, stop this from happening by regularly deep vacuuming your gravel or stirring it up. This prevents any pockets from being left in your substrate having the time to build up smelly gas.

A Dead Fish – Of all the causes of a bad smell emanating from an aquarium, a dead fish has to be the most common, devastating, and stinkiest. It is also probably the hardest to locate the cause of since dead fish can be hidden amongst plants, under rocks and caves, and even within a filter!

Luckily, the stench of a dead fish is the easiest to deal with; simply remove and wait for the smell to disappear. This usually happens quickly leaving no adverse effects on your aquarium. It is still, however, worth performing some aquarium cleaning just to be sure. Read our article on how to dispose of a dead fish respectebly.

Prevention is not totally possible since all fish will die at some point no matter how much you wish they wouldn’t. However, you can decrease the chances of a dead fish stinking up your aquarium by performing regular roll calls. Bear in mind this could be difficult with fish that are shy or nocturnal.

Rotting Plants – Due to the ease that rotting or dying plants are spotted this has to be one of the least common causes of bad aquarium odor. However, some people do not recognize the signs that their plants are dying or may hope they will come back to life.

The latter could be the case as long as there are only a few leaves that have turned a slimy black or brown color. However, if it’s all or most of the plant, it is highly unlikely and they should be removed. Pruning may well suffice for plants with a few brown leaves.

Prevention involves simply keeping your plants alive by providing them with sufficient lighting and nutrients. Snails, such as Trumpets, are also a great way to clear your aquarium of dead or decaying plants or leaves.

Please note that algae is also a plant and can be a huge cause of bad smells emitting from an aquarium. You can avoid excess algae growth by keeping your aquarium out of the glare of direct sunlight and by having a species of algae eater. Shrimps, snails and various species of Plecostomus are all good choices. Read our article on the Best shrimps and snails that clean your aquarium.

How Do I Get Rid Of A Bad Smell In My Aquarium?

If you haven’t managed to prevent your aquarium from becoming a stinky place to be anywhere near, then there are two things that you can do. The first is to identify the problem and deal with it quickly and efficiently as listed above, and the second to perform some emergency maintenance.

Emergency maintenance should take the form of cleaning your aquarium to remove the aftermath of a ‘smell disaster.’ As with weekly maintenance, this should always include; a partial water change, wiping the glass, cleaning the substrate, rocks, and decor, and also cleaning the filter.

Please note, however, that after you have removed the cause of the odor and cleaned your aquarium that it may smell worse at first. This is because you have dislodged all the rotting gunk that was causing the smell in the first place, and some of it will be floating in the aquarium. A 10 to 15% water change daily for a few days will soon take of this. To clean your aquarium glass there are 3 good methods. Read our reveiw of the 3 best ways to clean your aquarium glass.

Conclusion: Do pet fish smell?

As you’ve worked your way through this article, you may have noticed a common theme which is, that in order to prevent bad smells emitting from your aquarium, your maintenance needs to be spot on! This is due to most bad smells emerging in an aquarium coming from rotting organic matter which, yes you guessed it, a good maintenance schedule prevents from building up.

And to answer the original question, once and for all, pet fish do not smell of anything, rather the aquarium they live in does. However, this should and can be a pleasant smell like taking a walk in the country, or a pleasant stroll on the beach!

About the Author

Joanne Burn

Joanne has been keeping fish for many years both freshwater and saltwater and has been writing for fish keeping websites and magazines for even longer. Her fishkeeping knowledge, research and writing skill makes her an essential member of the fishkeeping forever team.