To anyone who’s had an aquarium for some time, this question may seem ridiculous; but to someone who’s just starting out, it’s a pretty common question. The thought is that if catfish and plecos clean the tank, should they count towards the number of fish I can have in my tank? The short answer is yes, they do count.
The reason is, when stocking a tank, you need to look at the bioload of the inhabitants. Let’s take, for example, Plecos and other algae eaters. These fish help make your tank look clean by eating the unwanted algae in your tank. But let’s consider that even though algae may not look great, it actually helps keep your water clean by removing nitrates and phosphates in the tank. Nitrates are an indirect byproduct of fish waste. So essentially, algae eaters, are actually eating the things that do help keep your tank water clean. So if anything, algae eaters actually may have a slightly negative impact on your aquarium’s chemistry. Now before you go and get rid of your algae eaters, while algae does help by using nitrates and phosphates in your aquarium, the amount is more likely negligible unless you have a serious algae problem.
You may be thinking, what about catfish? They keep the bottom of an aquarium clean. Catfish like Cory Cats may eat leftover food and clean the bottom of the tank, but they also produce waste themselves. In order for something like a Cory Cat to actually be cleaning your aquarium, it would need to remove more waste than it produces. They are often referred to as cleaners because they will eat the extra food that sinks to the bottom and would otherwise decay in the tank. In this sense, they clean your aquarium, but they still are counted when deciding how many fish you can have in your tank.
So if catfish and algae eaters don’t actually clean your tank, why are they so often sold as cleaners? Many times pet stores will sell these fish as cleaners if someone comes in asking about a problem. They may say, I have a lot of algae do you have anything that eats it. The store clerk may take the easy way out and sell them an algae eater when in actuality, reducing food for the algae, aka nitrates and phosphates, is the only way to get rid of it. By adding another fish, the bioload of the tank increases and more nitrates and phosphates are produced.
Thanks for reading and learning about “cleaner” fish. I hope you find this helpful and learned about more why “cleaner” fish aren’t cleaner fish at all.