Fish That Eats Poop – Do Fish Eat It?

As a fish keeper, you may be wondering if there are any fish that eats poop. This is a valid question, as it is important to know what goes into your fish’s diet. In this blog post, we will explore the topic of fish feces and whether or not they consume it. We will also look at some of the benefits and implications of this behavior. So, keep reading to learn more!

Key Takeaways

  • No freshwater fish actually eats poop
  • Freshwater plants are great for breaking down fish poop
  • Good filtration will help break down fish poop
  • Siphoning out large poop is recommended to keep toxic ammonia and nitrites down

Introduction To Poop-Eating Fish

Freshwater aquariums are dirty. There are dozens, if not hundreds, of different organisms and microbes that work together to make these contained ecosystems operate. Believe it or not, fish poop is essential for making these systems run efficiently and safely.

But what happens if you have too much fish poop entering the system? This can be due to overstocking, poor maintenance, inadequate filtration, or overfeeding.

Overloading The Nitrogen Cycle

As with anything, too much fish poop can overload the system with nutrients. When first starting a fish tank, ammonia must be added to the aquarium to initiate the nitrogen cycle. Over time, different microorganisms convert this ammonia into nitrite and, eventually, nitrate. This population of beneficial bacteria directly correlates to the amount of fish waste available and the subsequent levels of ammonia produced in the aquarium.

Simply put, more fish waste equals more ammonia and bacteria.

However, beneficial bacteria need to reproduce in order to compensate for higher ammonia levels, which takes time. A sudden or large raise in the level of ammonia in the system can leave toxic chemicals in the water column. This directly exposes fish, invertebrates, and live plants to potential ammonia poisoning, which can quickly become lethal.

The only way to prevent ammonia from overwhelming the nitrogen cycle is by removing fish poop and other wastes in the aquarium before they have the chance to break down.

Are There Any Fish That Eats Poop?

The easiest way to remove fish poop from the aquarium would be to have another fish that does the work for you.

Sadly, there is no aquarium fish that will eat the poop of another fish. And do not let anyone tell you differently! Less-informed pet store associates are very likely to try to sell you bottom feeders with the ability to clean up after other fish, but such a species does not exist.

Many freshwater fish and invertebrate species are sold as members of the clean up crew. While it is easy to assume that a ‘clean up’ crew member, especially a bottom dweller, will clean up fish poop given its assigned name, this isn’t true. Instead, these fish eat algae and other organic matter that makes its way into our systems, like decayed plant debris and leftover food. There is no benefit to a food source that has already been processed by another animal.

Fish that are commonly advertised as clean up crew members include:

From this list, Otocinclus eat algae. Corydoras, plecos, and loaches eat some detritus and natural algae but prefer fresh algae wafers and meaty foods instead. Freshwater sharks, like the rainbow shark (Epalzeorhynchos frenatum), might look like it eats fish waste and detritus off the substrate, but they prefer a fresh source of food instead.

Just because a fish has a flat stomach and barbels does not mean that it is a good member of the clean up crew!

Do Snails Eat Fish Poop?

Surely there is a species of snail that eats fish poop, right? No, freshwater snails do not eat fish poop either. Like fish, snails enjoy eating algae and other decaying organics. Some snails even like to eat live aquarium plants, though most are considered safe to keep in the planted aquarium.

Unfortunately, shrimp do not eat fish poop either. On top of eating algae and organic waste, some shrimp might even pick and eat parasites off of fish, but they will not eat poop.

At times, it might look like your fish or invertebrates are eating poop. In most cases, this is a case of mistaking fish poop for a piece of food and they’ll usually spit it back out immediately. But sometimes, fish might eat poop if other food isn’t available. This is a serious case of malnourishment and should be addressed immediately.

Why Don’t Fish Eat Poop?

If fish poop is abundant, then why haven’t aquarium fish evolved to eat it? At the very least, snails and other members of the clean up crew should have learned to eat poop over the years, right?

There is little to no benefit to eating poop. Poop is the remaining waste product of food, meaning that most of the nutritional value has been removed. Not only that, but it probably also doesn’t taste the greatest! If you’ve ever watched your fish eat, you may have seen it take a piece of food and then spit it back out. This is the fish’s way of tasting the food before it ingests it; and yes, fish definitely have preferences!

In the wild, it can also be dangerous to ingest poop. Many fish and invertebrates carry internal parasites which are sometimes excreted through feces. If another animal ingests this poop, then it will also be infected.

All in all, fish have evolved to avoid eating poop due to biological safety and appetite preferences.

What Breaks Down Fish Poop?

If other animals aren’t eating the poop, then where is it going?

As with anything that is organic, fish poop will naturally break down over time until it’s completely incorporated back into the ecosystem. Bacteria and other microbes will help eat fish poop and break down proteins that then get released as ammonia. The physical matter slowly falls apart and disintegrates over time, getting incorporated into the substrate and filter media.

Once in the form of ammonia or ammonium, live plants and bacteria can use these nutrients to perform photosynthesis and create food.

How To Keep Your Aquarium Clean

An accumulation of fish poop can lead to water quality issues and give your tank a dirty appearance. Because there aren’t any fish or invertebrate species that eat fish waste, it’s up to the hobbyist to manually remove the excess fish poop.

There are a few ways to make sure that your aquarium stays clean without having to rely on another fish to eat poop for you. This includes regular aquarium maintenance, controlling water flow, and incorporating live plants into your freshwater fish tank.

Regular Aquarium Maintenance

Fish are some of the easiest pets to keep, but they do require some care and attention from time to time. Once your aquarium has been set up and allowed to complete the nitrogen cycle, weekly or monthly maintenance is required to keep fish happy and healthy. How often you need to perform maintenance depends on the amount of bioload in the aquarium and how nutrients are being exported or processed.

For the most part, beneficial bacteria are efficient at their job of converting ammonia into nitrite and nitrate. However, larger particles, like fish poop, need to be manually removed.

One of the best ways to remove fish poop is by using an aquarium vacuum cleaner. This piece of equipment includes a plastic nozzle with long tubing and works through siphon physics. Check out the video below from Lifewithpets showing how to use a gravel vacuum.

Simply start a siphon by placing water into the nuzzle, lifting the nuzzle upwards so that the water can drain through the tubing, and placing the nozzle back into the aquarium before the remaining draining water can empty the tubing. This will create a continuous pull of water from the fish tank into another container (so long as the container is at a lower level than the nozzle). Alternatively, hobbyists can place the nozzle in the aquarium water and suck the end of the tubing until a circuit is created. Obviously, this can lead to some water getting in your mouth and potential ingestion (perform at your own risk)!

A regular vacuuming schedule can keep your tank clean and water parameters in check. It is not necessary to vacuum your substrate during every weekly or biweekly water change and some hobbyists choose to only do so when there are obvious accumulations of fish poop. Limiting substrate cleanings can also be beneficial when dealing with a sand substrate that can easily be kicked up and unintentionally siphoned.

Otherwise, 15-25% weekly or biweekly water changes will keep water parameters where they need to be. Water changes are especially helpful for removing nitrate, which can’t be naturally processed in freshwater aquariums without the help of live plants.

Water Flow

Water flow will not remove fish poop, but can greatly help with its collection of it.

The problem with fish poop is that it sinks to the bottom and gets stuck under rocks and other decorations. Once there, it can’t be easily reached with a gravel vacuum and it’s left to rot and contaminate the water. Adding additional water flow and circulation at all levels of the aquarium can help fish poop and other uneaten food from accumulating.

Additional water flow can be added through increased or greater filtration, air stones, or powerheads.

An aquarium can never have too much filtration, but it can have too much or too little water flow. For most setups, water flow should be moderate throughout both the length and height of the aquarium. There should be enough flow to keep objects from settling on the substrate and passing nutrients through live plants, but not enough to make swimming difficult for your fish.

Filter returns and powerheads help to create constant and random movement throughout the aquarium; a larger filter or several filters may be needed to create a desired random effect. At the same time, the filter intake may be placed in an area and level for the best waste intake while air stones can be used to bring circulation to dead zones.

Live Plants

One of the most understated ways to keep your aquarium clean and to get rid of fish poop is to keep live plants. Many inexperienced hobbyists think live plants are demanding in regards to lighting and water parameters, but there are many species that can survive even the worst beginner’s mistakes.

Live plants can process ammonium, ammonia, nitrite, and nitrate. Each nutrient facilitates a different physiological process for the plant, leading to growth and propagation. Because of their constant need for nutrients, many hobbyists typically keep their planted tanks at 20 ppm nitrate. Limited nutrients can lead to stunted growth.

While some fish keepers need to dose their aquariums with fertilizers to achieve these levels, others allow their fish to do the work for them. Fish poop is a natural and necessary addition to these systems, though too much can still lead to dangerous conditions.

Live plants are so efficient at processing fish poop and other organic leftovers that some hobbyists use them to help cycle their aquariums. This is often called a ghost cycle as the plants uptake nutrients before they can be observed through water testing. This is quantifiable proof that live plants, in fact, help take nutrients out of the water!

In addition to helping keep the fish tank clean, live plants also process carbon dioxide into oxygen and provide shelter and food for fish and invertebrates.

Final Thoughts

Sadly, there are no fish or invertebrates that eat fish poop. The only way to get rid of fish poop is by regularly cleaning the tank with a gravel vacuum, increasing and optimizing water flow, and adding live plants to help uptake excess nutrients.

While it might look like your fish is trying to eat poop off the substrate, it may be mistaking it for food. In this case, make sure that your fish is receiving adequate food and nutritional value as it may be hungry.

by Mark

Mark is the founder of Aquarium Store Depot. He started in the aquarium hobby at the age of 11 and along the way worked at local fish stores. He has kept freshwater tanks, ponds, and reef tanks for over 25 years. His site was created to share his knowledge and unique teaching style on a larger scale. He has worked on making aquarium and pond keeping approachable. Mark has been featured in two books about aquarium keeping - both best sellers on Amazon. Each year, he continues to help his readers and clients with knowledge, professional builds, and troubleshooting.

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