Fish to Avoid as a Beginner: Damselfish! Yes, Avoid Them!

Fish to Avoid as a Beginner: Damselfish! Yes, Avoid Them!

If you've spent any time researching your first saltwater aquarium, you've probably come across the advice to start with a damselfish. They're inexpensive, incredibly hardy, and available at nearly every local fish store. On the surface, they seem like the perfect beginner fish. Unfortunately, that advice is outdated. While damselfish can survive conditions that would stress many other species, their aggressive personalities often create long-term problems in a reef aquarium.

For beginner reef keepers, choosing peaceful, compatible fish is just as important as maintaining stable water parameters. A single aggressive fish can turn an enjoyable reef aquarium into a stressful experience for both the aquarist and every other inhabitant in the tank.

Why Are Damselfish So Popular?

For decades, damselfish were recommended because they are:

• Extremely hardy
• Very inexpensive
• Easy to feed
• Resistant to many beginner mistakes
• Widely available

These qualities made them attractive as a "starter fish" during the early days of the marine aquarium hobby.

However, what many beginners don't realize is that surviving in a tank isn't the same as thriving in a peaceful community aquarium.

The Real Problem: Aggression

Many damselfish become extremely territorial as they mature.

Once they've claimed a section of the aquarium, they often defend it relentlessly against nearly every new addition. This behavior can include:

• Chasing other fish continuously
• Nipping fins
• Preventing tank mates from eating
• Causing chronic stress
• Injuring smaller or timid fish

The result is often a tank where one inexpensive fish dominates everything else.

The Worst Offenders

While not every damselfish behaves the same, several species have earned a reputation for being especially aggressive.

Three-Stripe Damselfish

The Three-Stripe Damselfish (Dascyllus aruanus) is commonly sold to beginners because of its attractive black-and-white coloration.

As juveniles, they're relatively calm.

As adults, they often become highly territorial and may bully fish many times their size.

Domino Damselfish

The Domino Damselfish (Dascyllus trimaculatus) is another species frequently recommended simply because it's hardy.

Unfortunately, it often becomes one of the most aggressive fish in smaller reef aquariums, making future livestock additions difficult.

Blue Devil Damselfish

Its vibrant electric-blue colour attracts many first-time hobbyists.

Unfortunately, the Blue Devil frequently lives up to its name, relentlessly chasing peaceful fish throughout the aquarium.

"But Mine Is Nice..."

Every hobbyist has heard someone say:

"I've had a damselfish for years and it's never bothered anything."

And that's entirely possible.

Fish personalities vary, and some individuals remain relatively peaceful.

The problem is that beginners don't know which fish will become aggressive until it's too late. Purchasing a fish is always a bit of a gamble, but with many damselfish species, the odds simply aren't in your favour.

Why They're Difficult to Remove

Here's another issue many new hobbyists never consider.

Once a damselfish becomes aggressive, catching it can be surprisingly difficult.

In a reef aquarium filled with:

• Live rock
• Corals
• Frag racks
• Powerheads
• Decorations

Removing a single fish may require dismantling much of the aquascape and using a fish trap.

Many reef keepers simply learn to live with an aggressive fish because catching it becomes such a challenge.

Better Beginner Fish

Fortunately, there are many peaceful alternatives that are just as enjoyable.

Some excellent beginner choices include:

Ocellaris Clownfish

One of the most popular marine fish for good reason.

They're hardy, colorful, relatively peaceful, and adapt well to aquarium life.

EDIT (For those emailing us) 

Yes, Clownfish are technically damselfish (family Pomacentridae).

Our article wasn't referring to the entire family, but rather the aggressive species commonly sold simply as "damselfish" (Blue Devil, Domino, Three Stripe, Yellowtail, etc.), which are notorious for causing problems in beginner reef tanks. When shopping for damsels you won't go to the clown section.

Clownfish, especilly Ocellaris are the exception to the Pomacentridae rule. While they can become territorial, especially when paired or hosting an anemone, they're generally far more manageable than the classic damsels most beginners unknowingly bring home. In fact they are prob the best beginner fish. In our humble optionion. 

Firefish Goby

Known for their peaceful nature and elegant appearance, Firefish make excellent additions to community reef tanks.

Royal Gramma

Bright purple and yellow coloration combined with a generally peaceful temperament make them a favourite among reef hobbyists.

Watchman Gobies

These fascinating fish spend much of their time near the substrate and often form interesting relationships with pistol shrimp.

Banggai Cardinalfish

Calm, attractive, and easy to care for, Banggai Cardinals are another excellent beginner option.

Are All Damselfish Bad?

Not necessarily.

Some species are noticeably less aggressive than others, and larger reef aquariums can help reduce territorial conflicts.

Experienced hobbyists who understand fish compatibility may successfully keep certain damselfish as part of a carefully planned stocking list.

However, for someone's first reef aquarium, there are simply better and safer choices.

Planning Fish Compatibility

One of the biggest mistakes beginners make is buying fish individually without considering the final community.

Before purchasing any livestock, ask yourself:

• How large will this fish become?
• Is it known to be territorial?
• Will it compete with future fish?
• Is my aquarium large enough?
• Will it be compatible with corals and invertebrates?

A little planning today can prevent major headaches later.

Final Thoughts

Just because a fish is hardy doesn't mean it's the right choice for a beginner.

Damselfish have earned their reputation for toughness, but many species are equally well known for aggressive behaviour that can make maintaining a peaceful reef aquarium frustrating.

If you're building your first reef tank, focus on peaceful, community-friendly species that allow you to expand your livestock over time without unnecessary conflicts.

At Reef Supplies, we're always happy to help Canadian reef hobbyists choose compatible livestock and the right equipment to support a thriving reef aquarium. While we don't sell fish, we carry everything you need to keep your reef healthy, from premium test kits and salt mixes to filtration, lighting, pumps, and maintenance supplies. If you have questions about your setup, contact our team, we're always happy to help.