Unlike with freshwater aquarium fish, there aren’t as many saltwater aquarium fish to choose from for your fish only with live rock or reef tank. And those that are available often times have very specific requirements to successfully keep, and contrary to what others may say, not every reef fish should be taken from the reef to be cultivated or made for sale in the trade. There are plenty of saltwater aquarium fish to choose from that are hardy and take to tank conditions more readily, and plenty of captive bred species to keep things interesting. Below is a list of saltwater aquarium fish (in no particular order) that beginning fishkeepers should avoid due to their specific care requirements or the fact that they just don’t do well in the confines of a home marine aquarium.
Mandarin Goby (Synchiropus splendidus)
The Mandarin Goby (Synchiropus splendidus), also known as the Mandarin dragonet or mandarin fish is one of the most popular fish in the saltwater hobby due to its bright coloration and hovering swimming capabilities. However, this fish is one of the most finicky fish to feed and requires lots of live copepods, amphipods, and other tiny organisms in order to do well. These pods are usually found in well-established reef tanks, not beginner tanks. It is also a very slow and peaceful fish and as such cannot compete with other fish in a community tank. If you can find a Mandarin goby at your local fish store and can observe it feeding on frozen food such as mysid or brine shrimp, it might, and I stress, it might do well in a beginner tank, but that is if the tank has other peaceful and slow inhabitants for which competition for food doesn’t occur. While the Mandarin goby has recently been successfully captive bred by some of the major fish farms in the United States, and are fed commercial foods, most specimens are still wild caught. If you must have this fish, insist on a captive bred specimen and do your due diligence to watch to see the fish take frozen food in your LFS before you purchase it.
Twinspot goby (Signigobius biocellatus)
The twinspot goby (Signigobius biocellatus), like the Mandarin goby is very difficult to feed and is best avoided. The twinspot goby is a sand sifter and spends most of its time during the day sifting sand searching for live copepods and amphipods to eat. It is a very timid fish and will dart into its cave when startled. These fish are all wild caught and require a well established reef tank with plenty of live copepods in order to survive. While some twinspot gobies will eat frozen mysid shrimp and brine shrimp, getting the food to them in a community tank can be a challenge, especially if the tank is populated with more aggressive feeders. You will have to use a syringe or similar device such as a Julian’s Thing to target feed them several times a day. If you are going to take a chance with this fish, be sure that your sand bed is at least two inches thick and has plenty of live pods in the bed at all times. Not all fish species should be taken from the reef, and the twinspot goby is one of them.
Copper-banded butterfly fish (Chelmon rostratus)
One of the most common “maladies” with beginning saltwater aquarists is the proliferation of aiptasia anemones in the new aquarium. If you are keeping corals, aiptasia can sting them and even kill them. A natural solution to the aiptasia and other pest anemones is the copper-banded butterfly fish (Chelmon rostratus). Many aquarists purchase the copper-banded butterfly fish in an effort to rid their tanks of aiptasia anemones, and while the fish will do just that, oftentimes it will perish because aiptasia anemones are No. 1 on this fish’s menu, and when they are gone from the tank, the fish tends to starve. While this fish can be kept in the right aquarium under the right conditions under the care of the right aquarist, it may be too much fish for many saltwater aquarists and should be considered one of those fish best left on the reef. If you have an aiptasia problem, consider the Klein’s butterfly fish (Chaetodon kleinii). Most will dispatch your aiptasia (and any tubeworms and feather dusters) and eat frozen mysid shrimp.
Moorish idol (Zanclus cornutus)
The Moorish idol is another one of those fish that do best on the reef in the wild. While there are so many other fish in the trade, it causes one to wonder why this fish is still collected, and why folks still try and keep this fish. While the Moorish idol has been kept successfully in marine tanks, the vast majority of the specimens collected perish in captivity. They require very specific aquarium parameters that are the realm of advanced aquarist, and require large tanks of 200 gallons or more, not the realm of the beginning marine aquarist. If you like the look of the Moorish idol, consider the longfin bannerfish (Heniochus acuminatus), aka the poor man’s Moorish idol, as it looks very similar to Zanclus cornutus but is very hardy and easier to take care of. The Moorish idol is another species best left on the reef.
Yellow boxfish (Ostracion cubicus)
The yellow boxfish is very cute as a juvenile but will soon grow to up to 18 inches in length, necessitating a very large tank to house this species. This is a very timid fish that has another thing that should be taken into account when deciding on this species regardless of your expertise, and that is the fact that this fish, when under severe stress can nuke the entire tank, killing everything in it, including itself. That is because Ostracion cubicus possesses a chemical toxin known as ostracitoxin that it excretes via its slime coat when stressed, which can kill everything in the fish tank. If you decide that the cuteness of this fish is just too much not to acquire, ensure that all tankmates of this fish are of the peaceful variety, or better yet, house it in a single species tank.
Lionfish (Pterois volitans)
The Volitans lionfish is by far one of the most beautiful fish in the saltwater hobby, and also one of the most dangerous as its dorsal spines are filled with venom that can inflict serious pain on you if you are pricked by this fish. As such, this fish is best left to the expert marine fishkeepers. In addition to this fish’s defense mechanism, the lionfish will eat most any other fish that it can fit into its mouth and needs a fairly large aquarium of at least 120 gallons. Any lionfish species is not recommended for the beginning marine aquarist
Domino Damselfish (Dascyllus trimaculatus)
The domino damselfish, aka the 3-Spot Domino Damselfish, Three Spot Damselfish, Threespot Dascyllus is a member of the Pomacentridae family, and is an aggressive fish and as such is not really recommended for beginners even though the fish is more tolerant of varying degrees of water quality. As the fish grows its colors tend to fade dramatically from when it was a juvenile leaving their owners with an aggressive and drab fish in the future. This is a fish that is capable of bullying fish that are much larger than it and can be the most dominant and belligerent fish in your tank. If you must have this fish, or enjoy its bullying and bruising behavior, consider housing it in a tank of at least 30 gallons with similarly aggressive and belligerent tankmates.
Achilles Tang (Acanthurus achilles)
A member of the Acanthuridae family, the Achilles tang (aka Red-tailed Surgeon, or Achilles Surgeonfish) requires very specific water parameters and because of this is not recommended for the beginning saltwater aquarist. It is a fast swimmer that needs a very large tank of around 200 gallons in order to thrive, as well as strong and turbulent water movement.
Hawaiian Cleaner Wrasse (Labroides phthirophagus)
The Hawaiian cleaner wrasse is a fish that is best left on the reef because of its dietary requirements. It is not recommended for the beginning saltwater aquarist or the advanced aquarist. The Hawaiian cleaner wrasse cleans parasites, mucus and scales off other fish. Because of this, it will perish in most hobbyist aquariums, unless of course you have a 20,000 gallon living reef with plenty of fish with parasites. You can search the Internet for issues those who purchased this fish have had to deal with while watching them perish. Regardless if the local fish store says it is eating, everyone in the hobby should avoid this fish.
Picasso Triggerfish (Rhinecanthus aculeatus)
The Picasso triggerfish, also known as the humuhumunukunukuapua’a in Hawaii (it is the state fish) or Humu humu for short, is a reef triggerfish that while seemingly easy to keep requires three to five feedings each day, and because of this, is a gross polluter. Add the fact that this fish can grow to 10 inches, and your cute little juvenile can turn into an aggressive little monster. It will certainly attack smaller fish in a community aquarium, and it will rearrange your rockwork and sand bed and will bite heaters, power cords, and filter components such as intake or return tubes. A tank of 100 gallons or more is the ideal size for this fish, which may be too much aquarium for those just starting out in the hobby.