Saltwater Fish To Avoid As A Beginner – 14 Examples With Pictures!

We have all been there in the local fish store, mesmerized by this wonderful fish on the other side of the glass. We ask the store assistant some basic questions about the fish, and before we know it, we are walking out with our new purchase.

I am flabbergasted at how many times I have saved an un-educated aquarist from buying a fish they should not have, while in some of the un-ethical fish stores. I know they have to make money, but I hate to see animals suffer, and fish are no different.

By creating a fish stocking plan and researching about every kind of fish you would like to have, you can eliminate many of the problems newcomers to the hobby find themselves in.

Saltwater Fish to Avoid as a Beginner:

  • Catalina Goby
  • Hippo Tang
  • Angelfish
  • Bamboo Sharks
  • Moorish Idol
  • Groupers
  • Box Fish
  • Sweetlips
  • Mandarin Dragonet
  • Copperband Butterfly

Most of the fish on the list fall into one of the following categories, which may not create problems for you in the beginning, but will most likely end up with dead fish and you wasting some good money:

  1. Feeding Issues
  2. Aggression
  3. Disease
  4. Size

Remember these are recommendations for the ‘Beginner’. Once you have an established aquarium and have some experience, every one of these fish can be kept with ease so long as you provide it with the right environment!

14 Fish To Avoid As A Beginner

1. Catalina Goby

(Lythrypnus dalli)

Also Known As:
Blue Banded Goby

The Catalina Goby or Blue Banded Goby is a stunning fish with its deep red body and its vertical purple lines that shimmer when it swims.

These fish are native to the eastern Pacific Ocean from California through to Peru. They have been known to have a symbiotic relationship with the Long-Spined Urchin where they hide in the Urchins spines for protection.

In most aquariums, these fish would reach about 2′ to 2.5″ when fully grown.

Main Reason To Avoid As A Beginner:
These are a cool-water marine fish. Their natural habitat has a water temperature of between 60°F to 70°F. Unless you set up an aquarium specifically for cool-water marine fish they will soon die in your aquarium at 78°F-80°F.

2. Hippo Tang

(Paracanthurus hepatus)

Also Known As:
Regal Tang, Blue Surgeonfish, Palette Surgeonfish, Regal Blue Tang

One of the fish that became hugely popular after the release of ‘Finding Nemo’. This beautifully colored fish can always be found at the local fish store and many aquarists have these in their tanks.

They are an active fish from the Indo-Pacific region and is a voracious algae-eater. They will eat meaty foods, but they mainly can be seen picking away at the vegetation in your aquarium.

They are usually bought small but they can grow to over 5″ in a good-sized aquarium.

Main Reason To Avoid As A Beginner:
They are the most popular fish to develop Ich. Ich is a communicable disease that can wipe out your entire tank in a very short period of time.
Ich (Wiki Link) is usually brought on by stress and having a ‘Dori’ in a small, un-mature or over-crowded aquarium is a surefire way to see the ‘White Dots’ beginning to appear.

3. Angelfish

(Pomacanthidae Family)

All of the Large Angelfish Species

These are some of the most stunning marine fish you can ever find in an aquarium. Some of them change pattern and coloration completely as they mature. They grow to be very large fish and for most beginners, they are off the ‘Fish List’ due to the size of aquarium they need.

Most of the large Angelfish species can grow to over 10″ and require an aquarium of at least 200 gallons just to house one. This size of aquarium is very rarely advised to a beginner.

There are Pygmy Angelfish that are perfect for the beginner as they can live in much smaller aquariums. Those I recommend. The large Angelfish – Leave them for a bigger tank!

Main Reason To Avoid As A Beginner:
Even if bought small they will soon outgrow a small aquarium and become stressed. Stress only ever leads to death. Research the needs of the Pygmy Angelfish instead!

4. Bamboo Sharks

(Hemiscylliidae Family)

All of the Bamboo Shark family

These graceful and uniquely colored family of shark are seen in aquariums all over the world. They cruise around the sandbed looking for their next meal while giving us flashes of super unique patterns and colors.

These bottom-dwelling sharks are mainly found in the shallow waters of the Indo-Pacific region. Many of the sharks found in the local fish store are either juveniles of 2-3″ in length or even unborn sharks in their eggs. Those are super interesting to watch grow and hatch!

They are generally considered not safe for reef tanks, however, some aquarists have found them to be OK when introduced from eggs or very young juveniles.

Main Reason To Avoid As A Beginner:
They need a very large aquarium to thrive. They have been known to grow up to 3ft and are best suited to very large (+300 gal) sandy-bottom, fish-only aquariums. This size tank is not for the beginner.

5. Moorish Idol

(Zanclus cornutus)

Another fish brought into the limelight by ‘Finding Nemo’, however, this fish has the highest mortality rate out of all the cast.

The Moorish Idol is another native of the Indo-Pacific region leading solitary lives until mated. The pair will then stay together for life. Their diet in the wild consists mainly of sponges, coral polyps, invertebrates, and tunicates.

There are members of the Butterflyfish family that look similar to the Moorish Idol that does far better in the home aquarium, but again, you need a large aquarium to house Butterflyfish successfully. The Heniochus species is a good example – Wiki Link.

Main Reason To Avoid As A Beginner:
They are very difficult to get feeding well in a home aquarium, with most of them starving before being trained to eat. For the ones who do eat well, they will need a large, non-aggressive aquarium to be happy and healthy.

6. Groupers

(Epinephelinae Family)

Groupers are one of the biggest fish you can find in the wild and the species that seem to be sold in our fish stores are no different. There are some beautifully colored species seen in our stores and their small size and colorful markings hide a problematic fish for anyone but the expert aquarist with a very large aquarium.

There are many species of fish within the grouper family and they can be found all over the globe. The more colorful varieties found in our stores usually originate from the tropical waters of Indonesia, Sri Lanka, and Australia.

Groupers are a very aggressive species of fish with large mouths. Anything small enough will be instantly swallowed whole. Fish & invertebrates will certainly start to disappear as these fish begin to grow. Many of the groupers found in the stores will grow to over 1ft in length and thus need to be housed in very large, fish-only aquariums.

Main Reason To Avoid As A Beginner:
Small groupers will grow fast and begin to dine on your livestock. Do not be surprised if it becomes the only animal left in your aquarium.
Some groupers also have a mucus layer on their skin which they can release into the water if threatened or stressed. This is highly toxic to other fish.

7. Boxfish

(Ostracion Family)

These guys are one of the cutest fish you can find in the fish store and I fell victim to the purchase of one of these when it was less than 1″ long. 2 days later I found it dead on the side of my powerhead!

Anyways, apart from the delicate size when you buy them, these are another fish that come with problems hiding behind their pretty shape, markings and cute character. They will grow to over 15″ if they survive that long!

Boxfish are native to the waters of the Pacific, Indian and Southern Atlantic oceans where they can be found preying on algae, worms, small crustaceans, and fish. In the home aquarium, they can be very picky eaters and many starve in their first year.

Main Reason To Avoid As A Beginner:
Like the Groupers, these fish need to be cared for by the expert aquaritst with a large, mature aquarium full of tube worms.
Boxfish also have a mucus layer on their skin called Ostacitoxin which they can release into the water if threatened or stressed. This is also highly toxic to other fish.

8. Harlequin Sweetlips

(Plectorhinchus chaetodonoides )

Also Known As:
Spotted Sweetlips or Clown Sweetlips

This colorful fish has adapted its camouflage to replicate the look of poisonous flatworms in the wild. Found in the reefs of the Indian and Western Pacific Oceans these fish can be found from time to time at a local fish store.

Another fish that can grow large and having a carnivorous diet that will prey on small fish and Clean-Up-Crew given half a chance. Some aquarists have found them to be reef safe, while others have had them destroy their invertebrate population in a matter of days.

Main Reason To Avoid As A Beginner:
Apart from them growing to a large size they can be difficult to train them to feed. Dedication and the correct kind of environment can help to get these feeding correctly before they starve. Then you are just faced with them growing large. Another fish left alone for the big aquariums.

9. Damselfish

(Chrysiptera Family )

The Bullies of the Marine Aquarium!!

These are by far some of the most commonly available fish in our hobby, yet they cause more problems for their owners than any other family of fish.

Every member of the Damselfish family (Bar one – Get to that in a minute) is very, very aggressive and territorial. Many owners do not see this at first because Damselfish are still sometimes used to cycle aquariums – Do Not Do This!

If Damselfish are one of the first fish to be placed in your aquarium they will bully to death any fish you add after them. They are an absolute nightmare and good luck trying to catch it! Many aquarists have torn down complete aquascapes just to remove one Damselfish!

The only Damselfish I recommend is the Azure Damselfish (Link to I have two and they are beautiful and harmonious in the tank, however they were one of the last fish to be added.

Main Reason To Avoid As A Beginner:
Very aggressive and territorial. Fast swimmers making them nearly impossible to catch. NEVER add a Damselfish to your aquarium unless it is the last on your stocking list, and only then, after doing your research!

10. Batfish

(Platax pinnatus )

Also Known As:
Dusky Batfish or Red-Faced Batfish

One of the most unique fish you will ever see in an aquarium! The tall fins on the batfish give it a ‘majestic like’ glide as it moves through the water.

I have seen these in the stores as juveniles and they look fantastic but they grow very fast and they become much taller than most aquariums can accommodate. Fully grown these fish can reach 20″ tip to tip making them suitable for only the largest aquariums.

As they begin to reach adulthood this native Indo-Pacific fish will begin to prey on their natural food sources; Invertebrates, crustaceans and even small fish.

Main Reason To Avoid As A Beginner:
Their tall fins and size require them to be housed in large, deep aquariums to give them the ample swimming room they deserve. They may look small in the store, but they can soon outgrow your aquarium leaving you with a difficult fish to re-home.

11. Maroon Clownfish

( Premnas biaculeatus)

Also Known As:
Spine-Cheeked Anemonefish or Maroon Anemonefish

The Maroon Clownfish is one of the bigger clowns in the Genus. This native of the Indian Ocean is a slightly darker orange or red and their patterning can be beautiful.

The main reason they are on this list is that they are the most aggressive Clownfish you can buy. I used to maintain an aquarium with a 3″ Maroon Clown and he attacked me any time my hand went into the tank. Sometimes it would make me jump! I swear he waited to ambush me!

They are a hardy fish just like the other clowns and it can outlive a lot of your other fish. Add the aggressiveness of this fish and you could end up with an aquarium with just this fish in it!

The best way to own a Maroon Clown is to add them at the end of your fish stocking plan, this way he will not own the entire tank before any other fish are added.

Main Reason To Avoid As A Beginner:
Thier aggressiveness to you and other fish can make them a terrible bully, especially in a smaller tank. A larger, established aquarium is best when it is added last.

12. Anthias

(Pseudanthias Family)

Also Known As:
Lyretail Anthias, Jewel Anthias, Pink Anthias, Scalefin Anthias, and Squami Anthias

Anthias are one of my favorite reef fish, especially the Lyretail Anthias and I have a shoal in my own aquarium. However, it took me years to learn how to successfully keep them.

I recommend beginners to stay away from them for the following reasons:
They are very active and require multiple feedings every day – An Autofeeder is a necessity. Because of the extra feeding, they create more waste and your filtration needs to large enough to manage.

They do much better in a shoal, so a larger +75G aquarium is the bare minimum. They need lots of swimming space above the rock as this is the natural area they occupy in the wild, and they need a lot of rock to hide in.

If you can get them feeding and surviving well, the other downside is that each one can grow to 6″ and so a larger aquarium is best suited for Anthias.

Main Reason To Avoid As A Beginner:
Anthias need multiple feedings every day, lots of rock and lots of swimming space around and above the rock. They are a great shoaling fish, just save your money and wait until you have a larger tank with very good filtration then you will have no problem keeping them.

13. Mandarin Dragonet’s & Goby’s

(Synchiropus Family)

Also Known As:
Red Mandarin Goby, Spotted Mandarin Dragonet, Green Mandarin

One of the most attractive and sought after fish by every aquarist I have even known. The Green, Red, Ruby and Spotted Mandarins are always a talking point in anyone’s aquarium.

These fish are native to the Indo-Pacific region and will grow to approximately 2-3″ when they are in the right aquarium. They are very peaceful and docile fish which would make them perfect for beginners if it wasn’t for one major issue.

Their diet consists of eating Copepods. Some MAY be trained to take foods but many aquarists fail to get them swapped over before they starve to death. Each Mandarin will on average consume a pod every 5 seconds while awake and feeding. Because of this, you need a huge and constantly supply of Pods to successfully keep Mandarins.

Once your aquarium is several years old and seeded with a constant supply of Copepods will you be successful with keeping these fish.

Main Reason To Avoid As A Beginner:
A mature aquarium with a good supply of Copepods is the only way these fish survive. If you buy them before your aquarium is matured you will be on a journey to a starved fish.

14. Copperband Butterfly

(Chelmon rostratus)

Also Known As:
Beaked Coralfish, Beaked Butterflyfish, Orange Stripe Butterfly

An instantly recognizable marine fish to most people. This Copperband Butterflyfish is beautiful and looks great cruising around your aquarium.

Copperbands or CBB’s as commonly referred to can be found in the waters off Australia, Philippines, and Indonesia. They will grow to approximately 8″ when fully grown and require a good amount of swimming space.

This is another fish that can be terribly difficult to get feeding well in a home aquarium. Their tiny mouths make them difficult to provide food for before it is eaten by other fish, however, their unique mouth allows them to get into places the other fish cannot reach.

Their diet primarily consists of tubeworms, feather dusters, Aiptasia and coral polyps. A larger, mature aquarium is best suited to these fish, where over time they can be trained to eat fish food before they eat all the food they can find in their aquarium

Main Reason To Avoid As A Beginner:
Very difficult to get feeding well and many starve in a new aquarium. Many are bought to destroy an Aiptasia problem but then slowly starve once that food source has ran out.

Other Fish To Be Aware Of

Like any other part of this hobby doing good research before you buy is always the best way forward. This not only saves you money but also helps your new fish not only survive but thrive.

Here are some other fish you should research before buying:


They need a lot of swimming space! 75G minimum with open aquascape for just one Tang.


They may be feeding in the store, but the stress of a move to a new aquarium may make then terribly difficult to get feeding again.

Sea Horses

Very docile and slow swimmers. Best kept by an experienced aquarist in a species only aquarium.


Do your research. Some of them can be very territorial! Add them towards the end of your stocking list.

To Finish

Researching any fish before you buy is paramount. I have seen so many times where people buy a fish, get it home, drop it in the tank then ask the forums on how to take care of it. This is a very risky way to grow a saltwater aquarium!

Smartphones make it a lot easier to spend 10 minutes in a store researching the fish you are looking at but it is far better to spend the time and create that stocking list.

The next thing that I strongly recommend you always do is to Quarantine any fish you buy! It is simple, only takes a little more effort, but will save your aquarium from being wiped out by diseases like Ich or Velvet.

You can read more on how to easily set up a Quarantine Tank in my article here: Fish Quarantine. How To Be Ready In Minutes

Further Reading

These articles will provide you more help with your research:


Hi, I'm Richard and I have been an avid aquarist for over 30 years with a passion for Saltwater Aquariums. I love to pass on my knowledge to help others get the same amount a pleasure out of this hobby as I do. View my About Me page to find out more about me & my mixed reef aquarium.

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