Keeping “Difficult” Marine Fish

Keeping difficult marine fish - Copperband ButterflyThere are no real “difficult” fish; they survive just fine in the sea before someone comes along and collects them. They know what they need, and if we studied them in the sea, we would also know what they need, and it isn’t always about food (though most of the time, it is).

There is a reason different fish come from different places—why Moorish idols come from the South Pacific and not Coney Island, why mandarins come from the Philippines and not Bayonne, New Jersey. I have spent time underwater with most of the fish I have ever kept, and I learned more from swimming a few minutes with them than from all the articles I ever read about them.

Eating doesn’t equal thriving

We as aquarists have a large list of fish that some consider difficult. I say the fish are not difficult but that the aquarist is either lazy or just doesn’t know what that fish is supposed to eat. Not all fish will thrive on “normal” aquarium fare. Many will eat it, but eating something doesn’t always equate with thriving.

It is not the fishes’ fault if we can’t (or don’t want to) have the correct food on hand. I used to buy certain fish that had a bad reputation for dying because of not eating. I would figure that I am just smarter than anyone else, so I will just feed what I usually feed and the fish will be fine. But I was not as smart as I thought, and I lost plenty of fish with that type of thinking.

How many people buy a Moorish Idol and feed it pellets, mysis, and flakes and wonder why that fish lived only a few months to a year? How many mandarins die in people’s tanks even though they were “taught” to eat pellets or mysis? How many twinspot gobies are lost? Why do we lose so many copperband butterflies? Are Supermodels really that skinny? Oh, sorry, my mind drifts!

Some of those fish are not really difficult and are actually quite robust. They just have to be fed correctly.

Mandarins gotta have pods

Pellets and mysis are not proper foods for mandarins, and although they may eat them, they also need a bunch of “pods” (e.g., amphipods, copepods) every day or they will be short-lived.

A mandarin should live many years, not just three or four. As a matter of fact, I find mandarins to be among the easiest, lowest maintenance, most disease-resistant fish there are. But you can’t put one in a five-gallon tank that you started last Tuesday and teach it to eat ramen noodles while it watches Oprah Winfrey give away Cadillacs to homeless cats.

Mandarins need pods—or something like pods, such as newborn brine shrimp—and they need them not only every day, but all day. Fish such as mandarins (and pipefish) don’t have a real stomach and can’t store food. So any pellets you get a mandarin to eat won’t do it much good after the 15 minutes it takes for the food to pass through its digestive system and be eliminated as soon as it finds a pod.

I hatch brine shrimp every day to feed my mandarins and pipefish, and they are all spawning. My tank is large and very old, so there are plenty of pods, but I want my fish to spawn. That is why I feed them live, newborn brine shrimp in addition to any pods they can catch.

Copperbands want worms

Copperband butterflies are among my favorite fish, and I have been keeping them since the
‘70s. They also have a bad reputation, and many people buy them just to try to eliminate Aiptasia anemones, which is a shame because they are arguably among the most interesting and beautiful fish we have access to. They are also very hardy and live over 10 years. Unfortunately you won’t have any luck breeding them in a normal home aquarium, as it is just too small for them.

Copperbands are notorious for not eating for a couple reasons. They are almost never fed in stores because they don’t have the foods on hand that they need, and, like many fish with that skinny shape, they don’t stay healthy for long without food—not much fat on their bones, sort of like Paris Hilton. While copperbands may eat Aiptasia, they were obviously designed to eat worms. I have been diving with them, and that is what they need to eat. They will also eat mysis and clams, but worms should be part of their everyday diet.

Being mostly shell, mysis is not a suitable food for copperbands to eat on a daily basis. Fish like copperbands (or longnose butterflies) need meaty food every day, and that meaty food should be a “whole” food, such as a clam or, better yet, live blackworms. Some (very few) copperbands will eat pellets, and even fewer will eat flakes, but they will be short lived on that type of diet.

Don’t flake out!

Speaking of flakes, I realize that many hobbyists use them every day, and I know that businesses make money selling them. While there are some fish that will thrive on them—for example, fish in the damsel family will live fine on flakes—most fish will need supplemental feedings. Why? Because flakes are dry. Dry foods do not contain oils, as oils go bad (and stink). If I need to use flakes or pellets, I add fish oil to those foods to greatly enhance their nutrition. Remember, any food that does not need refrigeration and stays fresh for months is either full of preservatives or contains nothing good because vitamins and oil go bad without refrigeration.

Carnivores that crave fish

Then we have the larger carnivores such as the lionfishes and moray eels. Those types of fish don’t need variety; they just need fish—whole fish, not fish fillets or shrimp tails. They also don’t need goldfish. Small, whole saltwater silversides can be found in an LFS, and that is what those fish should be fed. Live, saltwater fish would be better, but unless you live near the sea (like I do), it would be hard to collect such fish. You people in Arizona, stop looking because you won’t be able to collect those fish where you live, so you need to move or keep kissing gouramis.

Some fish present special challenges

Many fish have problems living in home aquariums for different reasons. Lookdowns, panther groupers, parrotfish, and orbiculate batfish get huge. Moorish idols, besides having a diet that includes a significant amount of sponge, live in mated pairs (the ones I have seen anyway, but I’ve also seen a bunch of solo ones).

Some fish have other concerns that cannot easily be accommodated in a home aquarium. For example, shrimpfish live in the spines of sea urchins; flatfish, such as flounders, need fine sand to bury themselves in; and one of the most beautiful filefish, the orange-spotted filefish, eats coral polyps. Because of their beauty, they are unfortunately often sold, but very few people can keep one for any length of time unless they have a lot of coral to feed that fish.

Many parrotfish crunch up dead coral substrates for the algae they contain. Tangs and surgeonfishes can be kept successfully, but those types of fish always live in schools, sometimes with hundreds or thousands of individuals. For that reason, I believe they are always under stress in aquaria, which explains their “ich magnet” status.

The prettier, the harder to keep

Generally, if a fish is very unusual or very beautifully colored, it is harder to keep in an aquarium. I am not sure why that is, but the prettiest pipefish are very delicate, as are the best-looking, most colorful seahorses, filefishes, and a variety of tiny gobies. Those creatures can definitely be kept, but an investment of much more care and time is needed to satisfy their needs.

I also don’t know why brown, ugly fish seem to live forever. You almost have to run them over with a 1955 Oldsmobile, then put it in reverse and run them over again to kill them. When I was stationed in Vietnam, I had an ugly, brown catfish in a 10-gallon tank by itself. For a year, no one fed it, looked at it, performed a water change, or even added water to its tank. That thing lived until the week before I came home. It was in a couple inches of water. I am not sure how or why it died, but I did notice Oldsmobile tire prints on its back.


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About Paul Baldassano

Paul Baldassano has been in the hobby since the 50s and holds two aquarium-related patents. His current reef aquarium was set up in 1971. He is also an avid SCUBA diver and Vietnam veteran.


  1. This is a tricky one, because they are such beautiful fish and very hard to resist. If possible, let your LFS fatten them up a bit before buying one. The chances of an emaciated/very thin specimen surviving, even if its eating in the store, is slim, and you don’t want to spend a week or two fouling your tank with clams and mysis, putting the dietary needs of your other fish at risk, i.e tangs, who may be prone to outbreaks of marine ick or other ailments due to poor water quality and nutrition. QT is very important for these fish and a supply of clams on the half shell is a MUST to get them healthy enough for your display tank. That being said, they are definitely worth the effort, a very rewarding fish to keep and watch.

  2. Thanks for the laugh, Paul! The Oldsmobile references are a hoot!

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