Worst Marine Fish Species

From Microcosm Aquarium Explorer

Chaetodon ornatissimus.jpg
Ornate Butterflyfish, Chaetodon ornatissimus. Scott W. Michael
Gymnothorax javanica.jpg
Giant Moray, Gymnothorax javanica. Scott W. Michael
Paracentropyge venustus.jpg
Purplemask Angelfish, Paracentropyge venustus. Scott W. Michael

Species to Avoid: Our Red List Criteria

By Scott W. Michael

This list of Fishes to Avoid (or to Buy with Eyes Wide Open) is designed to help the beginning to intermediate aquarist avoid bringing home the wrong fish species.

Some of the fishes listed in this section can, in fact, make good aquarium inhabitants, but only under specific environmental conditions and/or in very large systems. The criteria we use in placing these fishes on a red list include:

  • Grows too large for most home aquariums;
  • Is highly predatory or territorial and likely to kill and/or eat other fishes;
  • Is hard to feed or has a poor survival record in captivity;
  • Is banned in some areas and a threat to local fish populations;
  • Finally, there are those animals that are a threat to their keepers and that do not make good aquarium animals under any circumstances.










Speckled Grouper

Moorish Idol










Red alerts on the big, the bad, and the ill-fated

Tales abound in the aquarium trade of naive hobbyists acquiring fishes they thought would be wonderful pets, only to find they have brought home an animal that is either unkeepable or a menace to others.

For example, I once had a young woman call me wanting to know what to do with her 4-foot nurse shark that could barely turn around in its 240-gallon (909 L) tank. Bought small, it grew into something she could not handle and that no one (including every public zoo and aquarium for hundreds of miles) would touch.

I have also met many aquarists who purchased coral-feeding butterflyfish only to discover that they could not get them to eat any of the foods available at their local pet store, no matter how hard they tried, coaxed or prayed.

This section is meant to help you avoid these pitfalls. While seasoned aquarists may disagree with my inclusion of one or more species, I can assure you that the track records for all the fishes included here are not acceptable, especially for the greenhorn or casual fishkeeper.

Included here are those that almost always have a difficult time surviving in an aquarium venue. Some—such as the butterflyfish that eat only live coral polyps—have very specialized diets, making it hard to meet their nutritional requirements. Some do not ship well, suffering from excessive stress during their long trip to the wholesaler and aquarium store. Some are very susceptible to disease. Others just outgrow the confines of most aquariums and cannot be expected to live their full life spans in a typical home system.

Ultimate Criterion

My ultimate criterion is to ask if there is a significant possibility that a fish of a particular species (or genus) will die prematurely because some special need is impossible or difficult to meet in captivity. If the answer is yes, it qualifies for this list. Whatever the reason, there are some species that are best left on the reef, or that should only be kept by aquarists with the resources and expertise to meet their very specific requirements.

As you advance in your aquarium skills and as more information becomes available on their care and feeding, some of these fishes may be worthy of another look.
Scott W. Michael


Why some fish are best left in the Sea

1. It will be DIFFICULT OR impossible to feed: Some fish, such as wild seahorses, need several meals of live foods each day. Others, such as the coral-polyp-eating butterflyfishes and sponge-eating angelfishes, have dietary needs that few aquarists could hope to meet.

2. IT GROWS TOO LARGE: Many reef fishes reach adult sizes that require very large tanks or facilities that only public aquariums can provide. Perfect examples are most of the sharks and rays.

3. IT is not likely to survive: Certain species, such as the Moorish Idol, have unknown keeping requirements or vulnerability to disease and very seldom adapt successfully to aquarium life.

Best Marine Fish Species

Reference: The 101 Best Saltwater Fishes
Image credit: SWM
Text credit: SWM