Breeding cardinal tetra.

[seangee]

I have a non intervention policy in my community tank and this means that over a period of a few years my tetra population gradually declines as there is too much light and too many corys for any chance of breeding in the tank. I keep 2 species; cardinals (Paracheirodon axelrodi) and glowlights (Hemigrammus erythrozonus).

My usual approach is to wait until each species gets down to 12 and then buy another 6. This time I want to make the groups a bit bigger and breed my own. I don't think this will be a problem for the glowlights because these are always spawning and the females are obviously full of eggs.

Right now I see no spawning with the cardinals and no sign off eggs. According to SF these are seasonal breeders (Jan - Feb). I have seen spawning behaviour but as I had no interest in breeding I have no idea what time of year. Is the season adjusted for northern hemisphere or do I need to do anything to trigger this? (Or does it just fall into the too difficult category?)

I am perfectly happy to practice with the Glowlights and just wait till winter (if appropriate) for the Cardinals. Right now I have 14 and 15 of each respectively so there is no rush.

 

[Byron]

Parachierodon axelrodi (cardinal tetra) is not easy to spawn. Czech aquarists managed to achieve this commercially over the last decade or so, but most cardinals in stores in NA at least are wild caught. Very soft acidic water, very dim light, and no other species in the tank might get you success. It sounds as if this is happening.

This species like all characins in SA is a seasonal spawner, at the start of the wet season when the rivers flood the surrounding forest for hundreds of square kilometers and the fry when they hatch have plenty of food because of this. This is why trying things like a massive water change with slightly cooler water will often trigger spawning among otherwise difficult species; it works very well with cories too. Do this on an overcast day (when rain/low pressure is in the forecast, as fish can detect atmospheric pressure very well). So that is the explanation of the time of year aspect. Get the fish thinking it is the wet season, and you may have better luck!

 

[Colin_T]

Drop the water temperature to 24C.
Feed them 3-5 times a day with a variety of food.
Do big daily water changes and gravel cleans to keep the water clean and to simulate rainfall (as mentioned by Byron).

After a couple of weeks the females should get really fat. Separate males and females for 4 days, then put them together in a 2 foot tank with a thin layer of gravel and some Java Moss.
Have blackwater in the tank. GH should be 0ppm. pH below 7.0 (around 6.0 to 6.5 is ideal). No lights on the tank and black out the back and sides.
Have an air operated sponge filter in the breeding tank.

Watch the fish and if you see them spawning (males and females will swim side by side into the plants), wait until they have finished and then move the adults out. Drop the water level down to about 6 inches but make sure the heater and filter are still covered in water. Cover the tank with a towel to stop any light getting in. Wait a few days and check each day for fry. When you see fry swimming about, start feeding them.

The following link has information on culturing live foods for baby fish. Start preparing food now because most of them take a month or more before they are ready for harvesting.
https://www.fishforums.net/threads/back-to-basics-when-breeding-fish.448304/

 

[seangee]

Do this on an overcast day (when rain/low pressure is in the forecast, as fish can detect atmospheric pressure very well).

That's an interesting fact which would never have occured to me. I did know about the temp changes with water changes and confirm that from my own observations (especially amongst the Corys) as I always add water that has been standing at room temp.

Have no way of naturally simulating a temperature drop at present so it will be a few months before I give it a go. (Of course with summer being such a fickle concept in the UK that may be weeks or even days ).

I do have a few easier species where I would like to up the numbers so I'll leave the tough ones till last, and I won't sweat it if it doesn't happen.

 

[PheonixKingZ]

That sounds like a tough species to breed!

Temperature and breeding fish, really don’t match.

And....Summer definitely doesn’t help! Good luck!

 

[Colin_T]

Fish are easy to breed. I set my tanks to 18C and they dropped to that in winter. In spring as soon as the water hit 22-24C they were all breeding and continued right through summer when the water was 30C.