You've got your aquarium beautifully balanced to be a healthy environment for the fish you've carefully selected, but you check the tank one day and you notice a number of tiny fry (baby fish) swimming happily around. This will upset that delicate tank balance, disrupt your carefully planned aquatic art and make more work for feeding, cleaning and maintenance. But what can you do to prevent unwanted breeding?
The Problems With Excess Fish
It may seem like "the more the merrier" ought to be the motto in any aquarium – after all, breeding fish must be healthy, happy and comfortable, right? Not necessarily. Many fish breed very easily and produce great numbers of offspring, simply because very few will survive to adulthood. The more fish in your tank, the more you will need to feed them, the more feces they will produce and the harder your filtration system will have to work. Smaller tanks can quickly become overpopulated, and a crowded tank will more easily host diseases that can kill every fish you have. Algae growth may increase as there is more organic material in the water from excess fish, and it can be difficult to reestablish a good chemical balance if your tank is overcrowded. For many aquarium hobbyists, unwanted breeding can be one of the biggest problems they face.
Minimizing Unwanted Breeding
Fortunately, there are ways to minimize the risk of unexpected fry appearing in your tank.
Buy only one gender of fish, preferably males.
If you don't have male and female fish together, there is less chance for baby fish to appear. This is especially true if you only add male fish to your tank. Female fish, however, could be pregnant when they are purchased, and depending on the species, may produce fry for several weeks or months after their last contact with a male. To be on the safe side, only opt for male fish in your tank.
Choose egg-laying species rather than live bearers.
Egg-laying species of fish generally need very specific tank conditions to hatch fertile eggs, and even if they are laying in your tank, it is unlikely the eggs will survive. Live bearers, on the other hand, incubate their young in their body and are very easy to breed, making it more difficult to avoid unwanted extra fish. Popular live bearers to avoid include mollies, guppies and swordtails. Egg-laying species that work well include tetras, bettas and barbs.
Adjust tanks conditions to make breeding less comfortable.
Some fish species are very sensitive to tank conditions such as pH level and temperature, and they are much less likely to breed when the tank is outside their optimal range. Deliberately keeping the tank at less than prime conditions may slow or stop any breeding activity, but it is a delicate procedure and may also make fish more susceptible to diseases.
Removing Unwanted Fish
When unexpected fish do show up in your tank, there are several ways you can remove them without taking drastic measures.
Let nature take its course.
If you have a large community tank with several species of fish, it is likely that many fry will get eaten by other fish. Minimizing hiding places the young fish can use and adding a more aggressive species or two to the tank will help with this natural population control.
Sell or give away extra fish.
Some pet stores may be willing to purchase healthy fry from amateur fish breeders, or you could sell or give away extra fish to other hobbyists. Also consider selling or giving away unwanted fry to people with other pets that may use the fish for food, or else contact a local nature center, elementary school or similar organization about free fish for educational purposes.
The one thing you never want to do with extra, unwanted fish is to release them into local ponds, rivers, lakes or streams. If the fish survive and breed in that type of unregulated environment, they can quickly become a hazard to native wildlife and may cause extreme problems in the ecosystem. Releasing non-native fish in these types of areas can also be a crime subject to hefty fines and other penalties.
You may not want every fish in your tank, but by taking thoughtful steps with the fish you choose, how you care for them and how you react to unexpected fry, you can keep your tank well-populated with just the fish you prefer.