Boxfish Factsheet: the odd, box-like fish family

Boxfishes are a rather large family of fishes. There may be over 40 different varieties, few of which are typically found in Pet Stores. Only a small sampling of all existing boxfish are caught and sold commercially. Their variety numbers are really even larger when one considers that many boxfishes may be called Cowfish or Trunkfish. The fish belong to the Ostraciidae family.

The common name more than likely comes from their appearance: an irregular box-like body. The body is, in reality, the bone structure and is covered with a very thin layer of skin. Because of the odd shape of the fins, boxfish are slow movers.

They are not agile and are very fragile. Keep this in mind when selecting other fish (companion fish). Bully-type fish should never be placed in the same aquarium as boxfishes. Doing so is really asking for trouble as the boxfishes will be constantly harassed by them.

Fish kept under such conditions will quickly get stressed and become diseased. They may also refuse to eat when they are stressed. Once this happens it is very difficult to get them to feed again. A fish that does not eat does not survive for very long and is even more susceptible to parasites, bacterial infections and other diseases.

Tetrosomus Gibbosus, commonly called humpback turretfish, helmet cowfish, camel cowfish and thornbacked boxfish

Feeding and Food

Because of their shy nature, slow swimming and relative clumsiness, boxfish tend to be outcompeted for food very easily, especially if they are kept with larger fishes or with aggressive ones. You always need to make sure that your Boxfish is eating.

When you acquire a larger specimen, make 100 percent sure that the fish is eating. Ask the store manager or employee to show you that the fish does indeed eat. Do not buy the fish if is not eating. It may be stressed out already. Larger and older fishes are harder to start feeding than younger ones.

You may wish to start feeding them cooked shrimp or something similar (scallop, fish roe, mussel meat, oysters and so on). It is best to feed other fishes in the tank first, and then concentrate on feeding your boxfish(es). Competition for food will be diminished if the other fish are satiated.

Boxfishes are in my opinion not beginners specimens. They should be added to the tank only when you have gained some experience in the hobby, especially experience with how to get fish that refuse to eat, to eat anyway.

Juveniles are easier to keep but very careful attention need to be paid to the fact whether they are eating or not. If they are not you need to find a food they like by varying fresh cooked fish foods until you find one that they care for.

Habits and Behavior

  • Boxfish are shy, some are very shy.
  • Boxfish are slow and always seem to have difficulty swimming.
  • Boxfish like to hide.
  • Live rock tanks are ideal for them.
  • They will disappear in the rocks if any danger is present.
  • They do not like strong water movement at all.
  • Boxfish develop skin diseases easily and are hard to treat.
  • Boxfish cannot be treated with copper. They have few or no defense mechanisms.
  • They swim slowly and move around in a odd way compared to other fishes.
  • They are not reef fish as they may pick on your corals.
  • They can sit still an area for very long periods of time. A normal behavior.

In conclusion, this is not the most easy fish to keep. It is certainly not a beginner’s fish. Making them eat and ensuring they do is very important if you are going to keep these fishes alive.

Think carefully about all this before you acquire one. Check what is already in your tank. If you have fast swimmers and aggressive fish, then boxfish are not for you.


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