Four Decades of Learning
I have also learned a few simple, but important, things as to how to get fish from mediocre health into excellent health. Much of this I learned from observing fish in the sea. If you have ever been diving, you will notice that wild fish almost always look better than captive fish. I think I've learned why this is. In the sea, fish eat mostly fish - not fish fillets, but whole fish. On any healthy reef, the portions near the base of the rocks are teeming with fry. Fish on the reef do not immediately eat all of these fry, as they would in a tank, because they are free for the taking at any time. Fry are not particularly hard to catch, so the larger fish do not have to work very hard for their dinner.
I believe that the reason wild fish are so healthy is because the diet of many of them consists of tiny fish, which consist of about a 20 percent oil as well as a healthy amount of calcium. All fish have a liver, which in a fish such as a shark, can take up almost a quarter of the animal’s weight. Almost all of that liver is fish oil. So a hundred pound shark can contain almost 25lbs. of oil.
As humans, we cannot use too much fish oil, as it becomes toxic to us in even fairly small doses. However, we do need some of it. Many fish, on the other hand, are used to getting almost a fifth of their diet as oil. As land based aquarists, we are often forced to feed our fish what is available in stores. Unfortunately, that usually consists of items such as squid, brine shrimp, clams, fish fillets, lettuce, beef heart, blood worms (not really worms but beetle larvae), mosquito larvae and angel formula. Most of these foods, as sold, are typically not available to reef fish in the sea, and none of them contain nearly enough Omega-3 fish oils. A variety of these commonly available foods offered to our fish will allow them to live long lives. But do we want our fish just to live, or do we want them to thrive, reproduce and be resistant to diseases - even parasites?
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Healthy fish are spawning fish. Yes, I know that not all fish will spawn in a tank, but the ones that will, such as most bottom dwelling fish and damsels, will only spawn if they are in excellent condition. Even if they do not have a mate, they will either dig a nest (depending on the species) or clean an area and chase other fish away. Fish in breeding condition rarely develop disease and tend to be resistant to parasites. If your fish are not spawning or making spawning gestures, they are not as healthy as you believe them to be. [Editor's note: This does not usually apply to tangs, angels or other egg-scattering fish.]
It is my educated opinion that all else being acceptable, if we can get fish oil into their system, fish will thrive. Those first blue devils I had in the 1970s spawned continuously for years, but only after I incorporated fish oil into their diet. So how do we get this oil into a fish? Well, there are a couple of ways. We can feed them fish fry like they get in the sea. However, unless we live near the ocean and want to wade into the water with a fine net every day, that would be tough task.
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15 year old fire clown with 15 year old bubble coral.
I have found a supply of tiny baby mackerel in Asian food stores. They are dried, and although my fish eat them, they are not crazy about their texture, which is similar to wood. Another method is to use flake food. Just put a drop of fish oil (available in any health food store, supermarket or
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) into a container of water and float the flakes on top of it. The flakes will absorb some of this oil and can then be fed to the fish. This method, however, will leave a colorful oil slick on the water surface water, and will cause the skimmer to stop producing foam for about an hour.
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Watchman gobies preparing to spawn (left) and seahorses begin egg transfer (right).
Another method for adding oil to the diet of fish is to put some pellets in a dry container and add the oil. The pellets will absorb the oil, and these can then be fed to the fish. This method is better than the flakes because the pellets will absorb more oil, and they will not create such a large oil slick. The best method is to feed something the fish love anyway. Live worms, such as California black worms, are available in many pet shops and can be ordered online. Do not confuse black worms with tubifex worms, which potentially contain much more harmful bacteria. Luckily for us, (and our fish) live worms contain a large amount of oil. I have been breeding fish for many years and have always been able to get fish into breeding condition very shortly by adding black worms to their diet. They should be used as a supplement only, and not as a main food, because they are very rich and the fish may not eat anything else if these are offered too often.