Siamese Algae Eater vs Otocinclus Catfish – What is the Difference?

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The Otocinclus Catfish falls into the same category as the Siamese Algae Eater. They both prefer eating algae more than anything else and therefore are outstanding solutions for your algae problem. Now the question is: Which one to choose?

This will mostly depend on what type of fish you are looking for. In this article, we are going to talk about the main differences of the two species and how to properly take care of them. Now we can assure you right at the beginning that these are not very demanding fish.

Therefore, it is a great idea for beginners to choose either of them. When it comes to the Otocinclus, there are 19 different species to choose from and they come from the rivers of Venezuela and North Argentina.

The Siamese Algae Eater, on the other hand, are native to Malaysia and Thailand. They are considered as the best algae eaters by most fish enthusiasts.

Below you can see the main differences in the appearance of the Otocinclus Catfish and Siamese Algae Eater fish:

Otocinclus Catfish

Otocinclus Catfish

Siamese Algae Eater

Siamese Algae Eater

Water Requirements

The Siamese Algae Eater loves to be around plants which also resembles its natural habitat. In the wild, it lives in tropical waters with weak current, yet they don’t require any water flow when kept in fish tanks. There need to be driftwood, caves or any ornament where the SAE can hide.

If you don’t see them looking for food, they are usually hiding somewhere in the aquarium. The temperature has to be set around 79°F which is a rule that applies to most tropical fish. They prefer an acidity of 6.5 to 7.0 pH and the water hardness to be 5-20 pH.

The Otocinclus Catfish comes from freshwater environments that are highly oxygenated. The things we said about the Siamese Algae Eater pretty much applies to this species too. They like to hide when stressed and spend most of their time in the bottom layer of the tank, feeding on algae.

The difference between them is that with the Otocinclus Catfish, you need to make sure the water is as clean as possible. Since they are rather sensitive to nitrite and ammonia, it is preferable to change the water once a week.

The perfect water parameters for them are 79°F temperature, 6.8-7.5 pH and 15dH water hardness. As you can see, there is a nice overlap that allows you to keep both species without any difficulty.

Minimum Tank Size

The Otocinclus Catfish is very small. They can reach only 1-2 inches in length when they reach adulthood. The optimal tank size for this species starts at 10 gallons which is indeed not much. In an aquarium of this size, you can fit in a maximum of 6 of them.

They will have enough space to swim around and live together comfortably. If you want to add more Otocinclus Catfish, each of them will need another 2 gallons. Look for aquariums that have a bigger surface area instead of going for the taller ones.

Siamese Algae Eaters are usually three times bigger, being able to reach 6 inches in length as they grow. For them, a 20-25-gallon tank is necessary. Every extra SAE will require another 10 gallons. Because of their social nature, it is better to buy 4-6 of them and let them thrive in a school.

They love to swim and eat algae together.

Feeding Requirements

Otocinclus Catfish are strictly herbivores, meaning that they only eat plant-based food. As long as they can find and eat algae in your aquarium, you don’t need to give them anything. Once they run out of algae, you can give them algae wafers that are available in fish stores.

You don’t have to buy these wafers if you don’t want to. If you can find some zucchini, lettuce or spinach in your kitchen, they will eat those too. These have to be chopped into tiny pieces in order to make them consumable for your Otocinclus.

Siamese Algae Eaters require a different diet as they are omnivores. They are not picky at all; you can give them almost anything and they will eat it. Just make sure to supplement their diet with some meat-based food. The additional protein intake will help them to stay healthy.

If you want your SAE to keep eating algae, then avoid giving them too much other foods.

Tank Mates

First off, Siamese Algae Eaters won’t bother Otocinclus Catfish in the ideal tank environment and vice versa. Of course, there has to be enough algae for both species in the tank. Both are peaceful, innocent species that mostly care about spending time together and looking for algae.

The rule of thumb is to not put them in the same tank with aggressive or territorial fish. There are plenty of them that would attack or eat them without forethought. The problem is usually with cichlids and Red Tail Sharks.

Both of these fish get along well with Danios, Angelfish, Guppies, Cherry Barbs and Nerite Snails.

Which is Better Algae Eater?

They are both exceptional algae eaters. The thing about Siamese Algae Eaters is they won’t eat algae anymore if you give them too much other foods. Otocinclus Catfish, on the other hand, eat only vegetables and algae. They never get bored of eating algae either.

You need to consider whether you want the small and cute fish or the bigger and more enduring one. Also, the Otocinclus is more sensitive to water parameters while the SAE is simply a hardy species. Although both are peaceful, the Siamese Algae Eater might annoy the other fish as it quickly swims back and forth.


In terms of difficulty, it is better to pick the Siamese Algae Eater because it is easier to take care of. Otocinclus Catfish are rather small and timid but they also do a great job cleaning up algae. Both species look awesome in groups.

They will provide you with lots of happy moments as you follow their routine. Hopefully, this article helped you decide which one is the right decision for you.

We gave you an overview about each one based on our experiences. If you find it hard to choose, then you should probably get both of them.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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