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Breeding Corydoras melanotaenia

by Mark Bryson
First published by the Paisley & District Aquarist Society (Scotland), Catfish Study Group (U.K.), and Scotcat.com
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First described by Regan in 1912,  Corydoras melanotaenia originates from Rio Manacacias, a tributary of the Rio Meta,  and from various other locations in Colombia. Body colour is bronze with a yellowish sheen. What catches your eye are the clean fins with bright golden/orange colouration. This colour is more pronounced when the fish are in good condition or ready for breeding.

I bought the fish at Huddersfield Aquatics 6th March 1999, on one of our club raiding trips south of the border. This is an excellent outlet that caters mainly for cichlids and catfish species, all wild caught. Four males (3.5cm) and two females, approximately 5cm body size, were purchased at what I thought was a bargain at £2.50 each.

When I returned home I set them up in a 45cm x 30cm x 30cm quarantine tank. Temperature 22ºC,
pH 6.5. Filtration was by an air operated Bio 45 sponge and a corner box filter filled with ceramic pipes and crushed coral (this prevents the pH from dropping too low). The tank also included a small glass trough filled with fine sand and planted heavily with Java fern. Java moss was weighed down and placed on top of a piece of slate (10cm x 15cm). On the slate I had attached small feet, which allowed the fish a hiding place and some security as I found them to be very skittish. They were fed at least twice daily on a mixed diet of live whiteworm, grindal worm, Tetra Prima & Tetra Tabi Min.

The fish were maintained in the above conditions until 4th July 1999. I then relocated their tank to a higher position in the fish hut, and doing this automatically increased the temperature by two degrees as the hut is space heated. I let things settle down for three weeks and then decided to have a go at getting them to breed. (It’s the old story, you talk to other aquarists who say they have bred Corydoras melanotaenia years and years ago without any problems, but they never really enlighten you as to how they did it). I was doing my weekly 25% water changes to all my tanks, but when I got to the melanotaenia tank I did a 40% change using water straight from the domestic supply, pH 8.3, temperature below 16ºC. Fortunately this had no adverse effect on the fish - quite the reverse, as 72 hours later (29th July), they had spawned. Water parameters at time of spawning were:  temp. 20ºC ,
pH 6.9.

Spawning:
Day 1.  I found the first eggs when I went out to the fish hut to feed the fish at 6.30 p.m. Eggs are ivory in colour and measure 1.5mm.
These had been placed at two different sites:
Site One  was on the front glass about 3cm from the water surface - approximately 150 placed in a group 3cm.in diameter with the eggs on top of each other, in the same manner as Corydoras barbatus lay their eggs.
The second site had double the quantity of eggs, laid in the same way, the only difference being that some of the eggs were caught up in some Java moss and only 10cm from the bottom of the tank.

For the purpose of this experiment I divided the eggs into four separate show tanks with water from the breeding tank. An airline was added with slow turnover to give slight water movement and treated as follows:
Site One: Spawning (surface) - small amount of methylene blue was added and then removed after 30 minutes by a 95% water change using water from the breeding tank.
Site Two: Spawning (bottom) -  I divided into two separate tanks and labelled them Site 2 and 3. 
Site Three: Eggs were left as they were, with nothing added to the water.
Site Four: Methylene blue was added and left for 12 hours, and then a 95% water change was done the following morning, using water from the breeding tank.

Day 2. All eggs had now changed colour to light tan, some were eyeing-up. Only six eggs fungused in all of the show tanks, and these were removed.

Day 3. 10 a.m. I did a water change to all three tanks after I removed a total of six white fungused eggs.

Day 4. 90% water change was carried out out in all small tanks, removing a couple of bad eggs. By the evening most of the eggs had hatched

Day 5. Water changes to all tanks removing any shells or dead fry. The fry from Site Two had started to die off and this had a knock on effect - by the time I returned later in the afternoon all fry from Site Two were dead.

Day 6. Still keeping Sites One & Three separate I transferred the fry into larger tanks (20cm x 12cm x 12cm). Bio-foam 45 sponge filter added. Feeding started with microworm. Prior to each feeding a 50% water change was done using water from the main breeding tank.

Day 7. All fry were looking well, and feeding now alternated between microworm and newly hatched brine shrimp, ensuring that 50% water changes were done prior to each feeding.

Day 10. I transferred the fry to 30cm x 20cm x 20cm tanks, and they were fed as much brine shrimp as they could eat, with a few feedings of grindal worms. Water changes were stepped up accordingly.

Day 14. All fry were moved into the same tank (45cm x 45cm x 30cm). I stopped feeding brine shrimp and concentrated on feeding grindal worms, Tetra Prima and Tetra Tabi Min. The fry were now beginning to look like the adults, the only difference being the fins had not coloured up.

Day 30. All fry were moved to 1015cm x 45cm x 30cm tank. Trickle filter filled with ceramic pipes and crushed coral powered by Fluval 4 internal filter. It is a very rewarding sight to watch 200-300 Corydoras fry moving about the bottom of the tank on the lookout for food.

Summary:  I normally like to keep eggs and fry with the parent fish, I believe fry grow bigger and faster in that environment. On this occasion I was quite glad that I did remove most of the eggs because I have never seen a single fry in the parents' tank. I know I didn’t manage to remove all the eggs at the beginning, therefore from my experience with C. Melanotaenia I have observed that they are egg and/or fry eaters. As to the experiment with methylene blue I’m not too sure what to do about that for the best. I think I’ll stick to the method of breeding corys that I have used quite successfully for the last few years, only changing things if the fish are a new species to me. If I do happen to get them to spawn,  I’ll normally remove most of the eggs and hatch them as above until I know the adults are not going to eat the eggs or fry.

*Mark can be contacted by e-mail m.bryson@ntlworld.com