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What is the worst saltwater fish to put in my aquarium?

Volitan Lionfish

The worst saltwater fish? I hesitate to call any fish a bad fish.

For nearly every fish I can put on a “worst saltwater fish” list, I can find examples of how people have had them successfully in their aquariums. Some of these are true success stories, and some are “no trouble… yet” stories.

There are exceptions to every rule, and in many cases, there are steps that you can take in planning your aquarium community which help to tone down the bad behaviors. So this isn’t intended to be a guide of fish not to put into your aquarium.


So what are the worst saltwater fish?

Based on my experiences, customers’ experiences, and observations, these are some of the fish that I personally avoid putting into most aquariums:


Maroon Clownfish

This beautiful fish is a centerpiece of many aquariums, and when it works out, a maroon clownfish attracts attention, especially when it does some of its odd behaviors.

However, the maroon clownfish has the reputation of being a nasty-tempered fish, and has earned its place on the “worst saltwater fish” list.

When it has staked out its territory, it starts to defend it aggressively. The aquarium owners and maintenance technicians I have spoken with say that they get bitten by this fish more than all other fish combined.

Fish added into an aquarium after a maroon clownfish has settled in are added at the owner’s risk.

They also have been known to push and rearrange the rocks in their aquarium. They also knock corals off of rocks, and move sand into large hills.

The most telling sign for me is that more customers have asked us to remove this fish from their aquarium than any other.


Yellow Tang

Fish-sellers don’t like it when I say this, because yellow tangs are popular purchases.

The yellow tang is a beautiful and colorful fish, and one of the most common ones in aquariums. It is an herbivore, and often helps to keep algae under control in a tank. You wouldn’t expect to see it on a list of worst saltwater fish.

However, from what I have observed, the yellow tang is also a bully fish, especially to other tangs or other fish that look similar to it. Adding a tang to an aquarium with an established yellow tang in it makes me nervous. When it works out well, it works out very well. But when it hasn’t, I have seen it can turn really bad really quickly.

If you want to add more color to the tank with another yellow fish, you can almost bet that the yellow tang is going to harass it, especially if it has established a territory in the aquarium. This rules out a significant selection of fish.

There are enough alternatives to the yellow tang which are typically more peaceful. For example, the Foxface Rabbit Fish gives the bright yellow and the algae control characteristics of a yellow tang with a more interesting look, and in over ten years, I have only seen one get aggressive with another fish one time (it was another foxface, which quickly submitted to the existing one, and they got along fine afterward).

Adding a yellow tang last sometimes helps to lessen the bullying. There are probably as many happy experiences with yellow tangs as there are not-so-happy. But with the available alternatives, why take the chance?



I like Lion fish. They are some of my favorite fish. They are gorgeous, and their personality can be a lot of fun.

However, putting a Lion fish into an aquarium draws a strict line between what you can and cannot have in an aquarium, which makes them one of the worst saltwater fish that you can add to an aquarium.

Lion fish are regarded as predators. Not because they are particularly aggressive, but because if it thinks something can fit in its mouth, then they think it is food. This includes other fish, shrimps, snails, crabs, and more.

I can tell you a story (I won’t put it in the blog) about a hair salon owner who suddenly lost three expensive fish and several shrimp in less than ten minutes after adding them to her tank with a Lion fish.


Trigger Fish

In 2006, I added my first trigger fish into an aquarium. The fish was a Clown Trigger that measured 10 inches long, and was going into an 800 gallon tank. I remember my boss at the time detailing exact instructions on how to add it.

“Do it exactly as I tell you, because it is big enough to take your finger off!”

Trigger fish are interesting to look at. Their shape, swimming, beauty, and personality can be charming. I remember a Titan Trigger that would swim around and squirt water toward passers-by.

But their teeth are there for a reason, and unless they are in a predator-only tank, it is usually a matter of time before they go after other fish and/or other animals, which is why I include them in the list of the worst saltwater fish.

What fish do you think is the worst saltwater fish? What else belongs on this list? Which of these fish have you had good experiences with? Leave a comment below and join the conversation.

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