Why your zebrafish may not be breeding
In preparation for a mutagenesis screening, my lab group and I set on a simple task: breeding zebrafish. Yet after eight weeks at the job, there were still no eggs—only frustrated scientists and less fish than we’d bargained for.
Following this frustration, I decided to take a crack at it on my own. Soon enough, I awoke to over 20 fry and 15 eggs.
Here are some tips to start your own fish farm:
- Make sure the hatchery’s holes are wide enough.
- Zebrafish eggs are typically two to three millimeters (mm) in diameter. If they don’t fall through the hatchery bottom, the adult fish will eat them. I recommend a three-way breeder, available at chain stores like PETCO and PetSmart. You can then float it in their regular aquarium overnight.
- Get an automatic light timer.
- These fish spawn in response to light, and should get around 14 hours of light plus 10 hours of darkness per day. I set my light to turn on at 9 a.m. and turn off at 11 p.m. so that eggs could be collected within 30 minutes of spawning (9:30 a.m.). Light timers are available at generic pet stores, but you’ll find much cheaper ones at hardware stores like Home Depot.
- Keep a proper male to female ratio.
- There should be less males than females. A 3:4 ratio is ideal. It’s difficult to tell the difference between the genders, but males are more streamlined, whereas females are generally larger with a wide frame (think “bloated”) and whiter undersides.
- Mind the temperature and pH.
- Temperature should be kept between 22 and 28 degrees Celsius (72 and 82 degrees Fahrenheit). pH should be kept around 7.0. I used distilled water to ensure neutrality as well as lessen the likelihood of introducing parasites.
- Vary their diet.
- Would you pass on mating after dining on fine live worms? The week before breeding, don’t overload your fish on food, but make sure they have a bit of everything: Tubifex worms, freeze-dried brine shrimp, bloodworms, and anything else tasty.
- Don’t stress your fish out.
- Do not attempt to breed them more than twice a week. The stress could take them down along with your research.
Zebrafish fry tend to stick to the aquarium glass. Scale is an approximation.