Dawkinsia rohani (Rohan’s Barb) Breeding Report and
Submitted by Patchin Crandall Curtis
Eight wild-caught sub-adult Dawkinsia rohani were purchased from The Wet Spot on 3/1/2018. They were placed in a new 125g tank that had just completed its fishless cycle in 28 days. One Rohan Barb developed ‘pinecone’ disease and died during quarantine. I assume it was because the tank was immature, and there was an ephemeral water quality problem as the tank settled with its increased bioload. It was especially unfortunate as the dead fish was one of only 2 females of the 8 leaving the remaining female to suffer the attentions of 6 determined males. They quickly put on good growth eating Repashy Soilent Green, North Fin Veggie pellets, and a variety of frozen foods with the occasional treat of Daphnia magna from Frank Cowherd.
Dawkinsia can take 12-18 months to reach sexual maturity. They are bold, active fish requiring a long run of 6’ and a large enough school to distribute sparring among males. They can be skittish jumpers but are otherwise unafraid of humans, quickly learning feeding patterns and even nibbling the fishkeeper’s fingers during feeding, but never in a way that hurts. They require pristine water, high dissolved oxygen, good flow, and cool water. A warm water change introducing water >76oF will send them into thermal shock. They enjoy cool water changes of 68-72oF.
The community tank is maintained at 74oF, has a gravel substrate, driftwood, and plantings of Anubias, Nymphaea ‘Red Lotus’, and various Aponogetons. The plants struggle because the fish are constantly nibbling at them as well as grazing on the driftwood biofilm. The water is soft (2-4d KH, 4-6d GH), charcoal filtered, and neutral (pH 7.2-7.6). 50% water changes are performed weekly, sometimes every other week if I’m traveling.
To net out the Rohan Barbs would require disassembling the hard scape, lowering the water to a few inches depth, and partitioning the tank which would unnecessarily stress out the fish not to mention the fishkeeper. Therefore, I decided to employ Ted Judy’s method of spawning barbs in the community tank using sinking breeding baskets. Ted made two excellent videos: one of spawning the Rohan’s, and the second of hatching and raising the fry. They can be found at: https://www.youtube.com/watch?v=pt9DyFDl4Ys for Part 1 and https://www.youtube.com/watch?v=Crf2MKQs2L8&t=8s for Part 2. Ted spawned his fish and hatched and raised the fry at 72oF.
On 3/10/2019, just over 1 year since obtaining the fish, the males started chasing the one female with purpose. Until this point, I had had trouble sexing the fish, but during the sparring the 6 males all raised their deeply serrated, spectacular dorsal fins. Once I could clearly see which fish were males it became readily apparent that the female was actually perceptibly rounder than the males. To spawn them, I quickly prepared a translucent shoe box, put in a layer of coarse gravel and 4 green yarn spawning mops weighted down in the middle with a stone so the strands of yarn would float upwards. The breeding basket was placed on the bottom of the tank. Some previous, unsuccessful experiments indicated that the fish preferred breeding baskets placed flat on the bottom to those placed in different orientation (flat, leaning to the side) at higher levels in the aquarium.
After placing the breeding box in the aquarium, the fish all scattered and stopped their spawning behavior. To give them time to settle, I went upstairs to make a cup of coffee returning about an hour later to see how they were doing. When I came back, the Rohan’s were no longer exhibiting any spawning behavior but one of the two Panda Barb males had taken up residence in the breeding box and was incessantly coaxing one of the females to join him. After a few successful clasps of the Panda Barbs I removed the breeding basket assuming that the Rohan Barbs had missed their window of opportunity. (Hint: I was wrong, so wrong).
I removed the spawning mops and gravel from the breeding basket, poured off some of the tank water, and pulled out a magnifying glass to inspect the bottom for eggs. I was able to see several dozen eggs. The eggs were clear to very pale yellow, translucent, and were not at all adhesive. The eggs were transferred into an extra large (6.6 gallon) Kritter Keeper with a fine gravel substrate, a sponge filter with airstone, a heater set to 74oF, java moss, oak leaves, and crepe myrtle bark to provide plenty of biofilm as a first food. There was no light fixture but the tank was placed in front of a bright window on the north side of the house. A burlap sack was used to filter sunlight reaching the tank.
On 3/12/2019 there were larval fish everywhere hanging on the sides of the acrylic tank. The larval fish were photophilic, preferring to congregate on the side of the tank toward the window. This is in contrast to Ted’s experience where he got much greater hatch rates from eggs kept in dark conditions. The fry were free swimming in another day or two. Once they were free-swimming I started to sparingly feed them vinegar eels largely relying on biofilm as a first food. After several days, I started feeding both vinegar eels and microworms more aggressively and introduced a mixed infusoria culture of rotifers, paramecium, euglenoids, and Blepharisma. The fry were immediately able to hunt and eat the rotifers. It took them a few days to grow big enough to eat the paramecium. It was very amusing to watch them develop paramecium hunting strategies. After about 2-3 weeks I started experimenting with baby brine shrimp holding off on adding significant quantities until I was sure the smallest fry could eat them. There were well over 80 fry in the tiny 6 gallon tank, and I wanted to prevent large differentials in growth rates among the fry. At about the one month mark it was apparent that there were three different species of fry present: the majority were long and slender and slower growing (these were the Rohan Barbs), about one third were more stubby and submarine shaped (these were the Panda Barbs), and then there was a single Rosy Barb, unmistakably deeper bodied than the others. Apparently right after I left for coffee, the Rohan’s got right down to business, followed by the Rosy Barbs, and only then the Panda Barbs. Either the majority of the Rosy Barb eggs were scattered outside the breeding basket, or they all got eaten except the one.
At the end of March when the tank got too crowded to house all the fry, I spent a couple of hours catching and sorting them, and deep cleaning two Kritter Keepers. All the Rohan Barbs (>60) went into one, and the Panda Barbs (~36) and the Rosy Barb into the other. I started to augment their diet with frozen food, pellets, and Repashy on ceramic dishes so they would quickly learn to recognize the feeding stations. All the fry continued to put on good growth. Eventually, I overfed the Panda Barbs fowling the tank and resulting in about 2/3 of them dying. I quickly did two massive water changes and saved about 15 of them. It’s so easy to make a mistake when such a small tank is so densely populated.
In mid-April I was able to free up the 55 g grow out tank and moved all the fry over to be reunited. Interestingly, the color pattern of Dawkinsia fry consists of gold-silver fish with vertical black bands. They are very long and slender and straightforward to discern from the pink and black, tubbier and stubbier Panda Barb babies once you train your eye.
As of 6/23/2019 and 3.5 months age, the Panda Barbs look like one-third to half-size juveniles with adult coloring even though sexing them is still not possible. On the other hand, the Rohan Barbs are smaller than the Pandas and still retain their fry coloration and markings. They take significantly longer to mature, not revealing their greater ultimate size and dramatic adult markings, but already hinting at the elegant, stream-lined form to come.