Tagged: selective breeding with fish


Young Albino Corey Catfish in community tank

You will need:

1 ten gal or larger fish tank  with filter                                                                                      1 gallon fish tank                                                                                                                                 1 glass vase

dual air pump or splitters  so you end up with 4 air lines fitted with air stones on them

Melathane blue (to keep fungus from growing on eggs                                         Melafix- anti bacterial- to keep fry alive

A razor blade and a fine mesh fish net.

The tank set up
1. Hatching vase
2. Nursery
3. Growing tank
(4. Community tank)

Breeding Corey catfish is a lot of work = but for me it was fun. Usually you discover you have a female  because she starts laying eggs all over the glass, plants and even in the gravel. There has to be a  male Corey cat fish in the tank to fertilize the eggs. The male curls his body around her head and shakes- depositing his sperm in front of her. She gathers this plus eggs as they come out of her- into her lower fins- she then swims to a spot – usually on the tank  glass and drags her under fins against the glass- sticking the eggs to it. They male will often swim over the eggs- depositing more sperm right on them. It takes around 30 min for the eggs to harden enough to scrape them off of the tank.

The white eggs are not fertilized- the tan color ones are.     After 30 min- or when you notice them- scrape them off with a razor blade- a few at a time because they will quickly drop to the bottom of the tank- collect them as you scrape with the fish net. (They will stick to the inside of the net.)

Have ready the glass vase 3/4 full with 2 drops Melathane Blue, 2 drops Melafix and water safe if using tap water- put eggs into vase- try touch them to the inside of the glass- they will stick naturally. They lay eggs for 3 days about once a month. Have a powerful air stone  running in the vase- it should be turned up strong enough to keep eggs from sitting still on the bottom. Use hose and stone to stir up eggs at least 4 times a day. On the morning of the 3rd day- or if you notice any hatch -you must change out as much of the water as possible with clean fresh water- that’s been treated with water safe conditioner. (the Melathane Blue will kill the new babies) Add in 3 drops of Melafix. The water depth  needs to be reduced to no more than 3″ deep. Reduce air stone to where it is still able to mix the water.  After 3 days they will hatch into microscopic 2/16″ long babies. They must swim to the top for a breath of air within a short time after hatching- you’ll notice them trying- it’s ok to place air stone under them to help them out. At the end of the 4th or 5th day change the water again- by pouring out as much as possible- without dumping babies- pour babies in a holding cup- clean inside of vase with  water and a mr clean magic eraser. Rinse and fill to 4″ deep. Use a spoon to scoop out un-hatched eggs(by now clumped together with fuzz growing on it) Bad eggs are totally soft, white and stay suspended in the water longer when it’s stirred . Good eggs are pretty firm and semi translucent off white and sink to bottom. After 6 days- whats left wont hatch.

On the 5th day start feeding them a tiny bit of  Koi food that’s been crushed into dust- a few times a day. Dirty water kills them fast so replace water as often as needed.

Expect 1/4 to 1/2 of them to die in first week and another 1/4 will die before they reach 1″ – this is normal.
After around 7 days- transfer them into the 1 gallon tank. make water about  2.5″ deep and have air stone running in water- but very gently. Continue feeding Koi food dust. When they are 1/3″ – 1/2 ” long they can be moved to the bigger tank.  At 3/4″ they can be transferred to a “grown up ” tank with the larger Cory.

tiny babies in 1 gallon tank. Throw in a little gravel as shown. To clean tank- raise water level to 5 ” and use a straw to suck up each baby and put in holding bowl. Suck up by placing finger over end before sticking in water- keep finger there and go in right above baby- lift finger for a split second and then put it back- Very quickly move to over bowl and lift finger again- the water that was sucked up will release. If your too slow- the baby will manage to swim out of bottom of straw.

The reason to remove eggs and hatch in a jar is Corey love to eat their eggs off  the glass in the tank- they will eat the new born babies as well.

If allowed to breed naturally- I would find maybe 2 a year. That’s it. With manual hatching- I averaged 25-50 survivors a month.

Pet stores sell Corey for $3.50-$4 each. Arrange in advance with a local pet store to sell your fish- they will pay you around 50 cents each for 3/4″ long.

Check with local laws- some states require stores to only sell fish from licensed breeders.

You might sell a few on Craigs list. Don’t do this if you have no where to place them. They are great for keeping Koi ponds clean.
Also- if you notice a cool mutation- like extra short fish- keep them separate and with 1 normal male and 1 normal female until you know what sex they are- keep only the eggs they lay. In about 1 year of selective breeding I created a whole new variety of Albino Corey Catfish. I called them “Stumpies”  At full grown- they averaged just over 1″ long. Normal are 2.5″ – 3″

normal size/shape Corey Catfish

My own selective breeding creation- Extra short Corey catfish.

Full grown- shown next to a quarter