Breeding & Fry

Breeding fish and rearing fry successfully

Accidents will happen….

Breeding fish and rearing fry is often initially almost completely accidental. The usual suspects for this are typical community live bearing fish: Platy, Molly, Guppy, Endler, Swordtail. Live bearers are very prolific, giving birth to 20-50  fully formed, live fry roughly every month. Their rate of reproduction means your tank could rapidly become overstocked. If your fry-rearing attempt is successful, what will you do with the babies?

Zebra Danio fry about 3mm long

During my first foray into fish keeping back in the 1980s I had the odd live-bearer fry appear and survive in my tank, but that was all. On my return to the hobby, surprise fry were an early introduction to breeding and rearing baby fish which has since become one of the most rewarding aspects of the hobby for me.

Breeding fish and rearing fry can be fun, but has its problems too….

Soon after rescuing Hermione I took a trip to a local fish shop (LFS) and bought six Gold Zebra Danios (Danio rerio). I kept them in a quarantine tank for about a month before introducing them to Hermione’s tank. Being a tad lazy, I didn’t immediately close down the quarantine tank: I turned off the lights, heater and filter, but it was a few days later when I finally went to empty it that I spotted what looked like tiny slivers of glass on the front panel of the tank.

An old school emergency food supply for unexpected fry…

On closer inspection I found the “slivers” were moving and realised they were very tiny newly hatched Zebra Danio fry. I decided to rear them, but had no idea what to feed them with as they were far too small for even crushed flake. A few minutes research taught me a trick I’ve been able to use again and again for egg layers’ fry: the yolk of a hard-boiled egg, squeezed into the tank water in tiny portions through a clean cotton cloth creates a cloud of microscopic particles, readily taken by very young fry. It’s an excellent standby for feeding tiny baby fish if you have no fry foods in the house.
I fed the Danio fry on egg yolk for several days while I bought and set up a brine shrimp hatchery to hatch live baby brine shrimp, which the Danios eagerly accepted. The babies grew rapidly and after a few more days on live baby brine shrimp four times a day, they moved on to take commercial flake foods. After a couple of weeks I was able to count them and discovered I had around sixty of them.

What happens when fry grow up?

I was fortunate that a local shop agreed to take most of them, but it was a lesson learned. Breeding fish and raising fry is fascinating and fun, but not for the faint-hearted. It’s far better to breed fish only when you already have a definite new home for the babies than to take a chance on it.

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