Q. I have a problem with a breeding pair of angelfish. The female appears to be filled with roe, but seems to be suffering from some sort of swim bladder problem. She is unable to swim or eat, and just floats helplessly at the surface of the water. The pH in the tank is 6.5, the total hardness around 50.0 parts per million, and ammonia, nitrite and nitrate are all within acceptable ranges. Is there any way to cure this problem? Finally, if the female should die, is there any chance of getting the male to breed with another female?
A. I am of two minds about your letter. On one hand, I am delighted to learn that this column has readers in Australia. On the other hand, I hate queries about swimbladder problems because there is no consistently successful treatment. Most swimbladder malfunctions are caused by some sort of physical trauma. In fancy goldfish, which are more susceptible to swimbladder complaints, abrupt temperature changes appear to be an important causative factor. With cichlid fish, physical trauma, such as a sharp blow to the flanks in the vicinity of the pectoral fins, often results in injury to the swimbladder. However, the usual symptoms of such trauma are loss of buoyancy rather than the reverse.
The symptoms you describe suggest that something within your fish’s body is generating an excess of gas. Bacterial activity can have just that effect, which is also consistent with your fish’s full-flanked appearance. I would thus tend to believe a bacterial infection is the cause of the problem.
Unfortunately, there is no way of treating this sort of systemic infection in a fish that refuses to eat fish food. The antibiotics likely to prove effective against the pathogens in question are not absorbed across the gill membranes and skin. Nor are such drugs likely to be swallowed if simply added to the aquarium water, for freshwater fish drink very little as part of their strategy to maintain a viable internal salt/water balance. It is thus a virtual certainty that by the time this letter appears in print, your fish will have expired.
Happily, the widower’s prospects of finding a new mate are excellent. One of the more persistent myths about cichlid fish behavior is that monogamous species “mate for life,” rather like parrots and geese, and in consequence, cannot be expected to establish a pair bond with a new partner should anything happen to the other. In point of fact, monogamy in nature for the overwhelming majority of cichlid fish describes a bond between one male and one female of the same species that persists for the duration of one reproductive episode. The exceptions are species that jointly defend a limiting resource, such as a cave, over a protracted period of time — such as the Julidochromis species of Lake Tanganyika.
I suspect the basis of this myth is the simple fact that as long as each sex’s respective reproductive cycle is in synchrony with the other’s, there is no obstacle for a given pair of cichlid fish to respawn repeatedly. The constant supply of food guarantees that this state of affairs is more likely to occur under aquarium conditions than in the wild. However, to observe that a pair may respawn in captivity by no means implies that either partner will, in consequence, refuse another consort.
Indeed, the behavior of angelfish, discus, uaru and severums in captivity strongly suggests that these cichlid fish routinely change mates in nature. When pairs of these laterally compressed cichlid fishare kept together for an extended period of time, it is quite common for the male to become completely indifferent to his mate, to the point of not fertilizing her eggs! Commercial breeders are often obliged to engage in a regular program of mate-swapping in order to assure male cooperation in the business at hand. So, assuming that you have selected a healthy female and conditioned her well before introducing her to your male’s tank, I predict that you will soon be raising baby angelfish again.