It may seem a little embarrassing to ask, but in case you were wondering, we’ll answer it – Do fish eat poop, and if so, what fish?


Do fish eat poop?

They might, but they probably don't. You may sometimes see a fish nibble on poop from other fish, and fish do have a tendency to eat whatever they see floating in the water column – but they also have a tendency to spit non-food items back out (including poop). Some animals, such as rabbits, may eat faeces as a “2nd round” of nutrition and it’s entirely possible that a fish might ingest some poop that they mistook for other foods – but this isn’t necessary for their nutrition and isn’t likely to help out with your tank health (we’ll talk more about this soon).


Platy fish  

Above: The Platy Fish (Xiphophorus sp.) - Good at making poop, not good at eating it.


What fish eat poop?

As far as we are aware, there are no freshwater fish that have poop as a necessary part of their diet. Some fish such as Corydoras and Plecostomus catfish are said to eat poop – but even if they did, they still require feeding just as any other fish would. Although it might depend on what fish processed it, the products left in poop are mostly waste – meaning there isn’t much left that’s useful to the fish that decides to nibble on it.


But won’t their poop-eating help my tank health?

It sounds like a cool idea, but unfortunately it isn’t going to do a whole lot for your water quality. As mentioned above, even if a fish does eat poop, it still requires a sufficient high-quality diet. This, mixed with waste being a natural part of any living being, the fish eating the poop is still going to poop! Only they’re going to add to the amount of poop in the tank, as they are extra fish that still need to be fed.

Not only that, most of the nitrogenous wastes (such as Ammonia) are actually excreted via the gills, not poop[1][2]! While it’s still important to remove physical wastes such as poop from the tank when possible, Ammonia production will still happen regardless of how much poop is produced or eaten.


How do I get rid of poop, then?

There is something that will eat poop – a good siphon. This is a key method of removing debris from your tanks water column and substrate. Regular cleaning of pre-filter sponges (our personal preferred method) and mechanical media are also important methods to remove debris build-up, thus removing excess waste and allowing for better flow of water to your beneficial bacteria (which are essential for converting that Ammonia).


bristlenose plecostomus pleco

Above: The Bristlenose Pleco (Ancistrus sp.) - Also good at making poop, still not good for eating it.


In Conclusion

Whilst there aren’t really any fish available purely for the purposes of eating poop, fortunately poop-eating fish wouldn’t be that useful for your tank health anyway. You can still add those Corydoras or Plecos (provided your tank is suitable) as they are fascinating fish to keep, but unfortunately they won’t quite do the job of cleaning up (that part is up to you).

We hope that this article may be of some help when making the decision of whether you add some poop-eaters! Have any questions? Feel free to Contact Us!


[1] https://cyber-aquaculture.wikispaces.com/The+Nitrogen+Cycle
[2] http://vetsci.co.uk/2010/05/15/comparative-nitrogen-excretion/