Surgeonfish in Marine Aquariums: How Many and Why?

by | Feb 16, 2023 | Fish | 1 comment

Acanthurus leucosternon

I’ve always loved aquariums full of fish; it looks like you are diving in tropical seas. I’ve always had a lot of them, and I know that the most important thing is knowing which ones you can insert and give a good life to.

In the end, it’s all an exercise of equilibrium and proportions. A big fish in a small aquarium is not that nice to see and it’ll make your aquarium appear even smaller than it is, regardless of the beauty of the fish. Moreover, many fish that are too large for their space, such as some surgeonfish, can become very aggressive can attack other fish, or they start to get sick frequently, infecting other specimens too. Then you have to consider the biological niches: it would be ridiculous, for example, to add 20 angelfish and then complain that no one is swimming in the upper part of the aquarium. You also have to consider the colors, because some fish get very aggressive towards specimens with similar liveries. And shoal fish have to stay in shoals… and so on. But let’s continue with order.

Is there a maximum number of fish that can be kept in a marine aquarium? Not exactly, but if you want to obtain the maximum from your aquarium, you have to study, know, and respect the fish. Choose them wisely.


Let’s start with a classic: surgeonfish. These fish are very beautiful, tireless swimmers, and great seaweed eaters. They’re quite big and need their space for swimming, so they prefer rectangular rather than square aquariums. They don’t like to have more than one in the same aquarium because of the small space they’re allowed to have. So the limit in this case is simple, if you have less then 300 liters avoid surgeonfish. It will be better both for the fish and your tank, and smaller fish will make your space looks more balanced.

Zebrasoma can adapt to a space between 300 and 400 liters. Ctenochaetus need at least 400 liters to start, and Acanthurus and Naso will need 500 liters, but if your tank is rectangular and you don’t have many animals, they could possibly be okay with 400 liters. In any case you have to study animal by animal. A Sohal, for example, although it’s an acanturidae, should never stay in an aquarium of less then 750 liters.

Remember that surgeonfish need to eat seaweed, a lot of seaweed, from the nori that you buy at the supermarket to those packaged for aquarium fish, and also plant-based granular food.

[Translated by Agnese Poggi]

  • danireef

    Danilo Ronchi, aka DaniReef lives in Italy where he is hydraulic engineer, but starting from his love for reef aquarium and photography, he began to write about marine aquariums from 2006 and now he's published his first book "Marine Aquarium". From 2007 Danilo writes on his blog where publishes articles, pictures, product reviews, aquariums coverage, reportage and history of his tank. Now he's happy to be part of

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1 Comment


    I understand that there will be a lot of studying to do.


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