The Best Diatom Eating Fish for Your Tank – A Full List

At this point, you must have already heard of diatoms – a group of microalgae that thrive in glass houses and every aquatic environment available. Hence, it’s no surprise that a typical tank for pet fish is the perfect condition for their communities to grow. 

Though most of them are not dangerous, there are still cases where studies report toxin production from some diatom species, affecting both animal and human health. One case in point is Pseudo-nitzschia – the root cause of domoic neurotoxin that can cause chronic diseases in humans, shellfish, and marine mammals.

Fortunately, these diatoms are not unbeatable – the list of diatom eating fish options below can keep your tank in optimal living condition! Keep scrolling for more. 

What Is The Best Diatom Eating Fish?

Siamese (Crossocheilus Oblongus)


Siamese is lauded as among the most efficient diatom-eating creatures. Why? It can consume varied algae types, not narrowing its diet down to just one or two categories like some other fish!

Another reason they have become so popular is that siamese can detect and hunt diatoms/algae ignored by most other fishes (one example is blackish-beard algae). 

In general, siamese is quite peaceful and demands little care. Thus, professionals deem them a perfect option for newcomers/beginner hobbyists, as they can learn how to control the tank much better. 

From our experience, siamese needs a tank of at least 30 gallons, preferring water of 6.5-7 pH with temperature fluctuating between 75 and 79 degrees F. Keep these parameters in mind to ensure the best outcome! 

Chinese Algae Eaters (Gyrinocheilus Aymonieri)

Chinese Algae Eaters

Like siamese, taking care of Gyrinocheilus is also fairly easy. A tank of 30 gallons is enough for them to develop, though you should note that their maximum size can be pretty impressive (10 inches). 

They also tend to grow more aggressive over time, which is why you should think twice about keeping delicate fish species in the same place as them. 

But on another note, their aggression might be a good sign – since Gyrinocheilus is the only diatom-eating fish that can fight against semi-aggressive and large species (ex: cichlids). 

Regarding their diatom consumption, we must admit that Gyrinocheilus might not be the best algae killer out of this list, as they become lazier when their size increases. 

Nevertheless, during their earlier stages, Gyrinocheilos can prey on many different diatom/algae types – a capability you should still make use of at the end of the day!

Chinese algae-eating fish prefer water of 6.8 to 7.4 pH, with 8-10 KH. Warm water temps suit them best, and you should also prepare herbivorous diets to speed up these fish’s growth and boost their algae-feeding.

Twig Catfish

Twig Catfish

Twig catfish are known for their thin and long bodies, which can grow to a maximum length of 4 inches. 

In most cases, they are pretty docile, compatible with most peaceful species out there, like livebearers and tetras. However, with larger fishes (like cichlids), you should prepare them some hiding places – since their tendency to get bullied is pretty high. 

Letting them live alone is fine, but experts discover that twig catfish will grow better with a tank mate. Hence, it would be great to give them at least one companion – and keep them in pairs as frequently as possible.

The required tank size is 12 gallons (minimum). Its water should be moderately soft, with a 6 to 8 pH level. 

Twigs can feed on almost every algae type, but that does not mean you should leave them on their own. Preparing them with some supplemental feeding diets is still a must! 

Otocinclus Catfish

Otocinclus Catfish

As the smallest ones on our list, otocinclus only grows to 2 inches at maximum. Their overall appearance bears a lot of striking resemblance to Chinese algae eaters, but the two’s habits and behaviors differ quite a lot. Otocinclus is much calmer and more peaceful. 

For the most part, they can adapt well to community aquariums and easily make friends with bottom-feeders. Aggressive and large species are not suitable tank mates for them, though.

These fish are not demanding in nature, and taking care of them is moderately easy. Still, they do require tanks no less than 30 gallons, which ensures enough algae for them to consume (and also, they are better kept in large-sized schools). 

Professionals learn that Octocinclus prefer 6.5 to 7.5 PH level but can still tolerate some fluctuations in the water chemistry. Brown algae/diatom is their common food – all the more reason to purchase Otocinclus if your tank is filled to the brim with these diatoms.


1. Will Diatoms Vanish By Themselves If There Are No Diatom-Eating Fish In The Tank?

We have received this question from many readers. In short, our answer is Yes. Like any natural organism, they can still have a natural death without any interference on your part. 

However, this process can either be super quick (only two weeks) or take months, depending on the algae type. And if you don’t remember, let us remind you: one week is more than enough for harmful diatoms to affect the plant’s and fish’s health!

That’s why buying the fish listed above is always recommended, removing these harmful substances as quickly as possible. 

2. Can My Fish Get Sick Due to Eating Diatoms?

Aside from those we have listed, yes. Not all fishes consider diatoms their ideal food, after all. And as previously mentioned, the toxin released from them can even cause death.


What is the most suitable diatom eating fish for your house aquarium? Our insightful article has listed some promising options, delivering quick overviews of their basic required conditions for living. Remember those tips to keep your tank algae-free!

For more questions and guidance, you can always write to us.