Spawning Report: Pethia conchonius (Rosy Barbs)

Pethia conchonius (Rosy Barb) Spawning Report

Submitted by Patchin Curtis

This report describes the spawning and raising of fry from 4 (2 male and 2 female) tank-raised Rosy Barbs purchased from The Wet Spot in April, 2018. The Rosy Barbs had been kept in a 125g community tank for over a year with a school of Panda (aka Melon) Barbs and Rohan Barbs. Previous spawning attempts by placing breeding baskets in the community tank had yielded large numbers of Panda Barb and Rohan Barb eggs mixed in together, but only a single Rosy Barb fry. Therefore, I decided to take a more intensive approach with the Rosy Barbs described below.

Day 1: On 6/18/2019 two 10 gallon tanks were set up with bare bottoms and small corner box filters containing some charcoal and ceramic filter media. The tanks were filled with clean, cool (74oF), neutral (pH 7.2-7.4), soft (3d KH, 5-6d GH), charcoal-filtered tap water. Two breeding baskets were prepared consisting of a translucent plastic shoebox-sized container filled 1-2” deep with marbles in one and pebbles in the other. Some yarn spawning mops weighted down so the yarn fibers would float upwards were placed in each box. The breeding baskets were added to the tanks.

The tanks were not heated. Temperatures ranged from 71oF during the day to 68oF at night, except upon water changes which were done with water at 74o. No lights were placed on the tank. The tanks were placed on the floor in front of two large French doors on the north side of the house giving them exposure to bright, indirect light. The moon was at half-moon, so the nights were fairly bright as well. A front had stalled over the region, and multiple rain showers moved through over the next several days.

Once the breeding tanks were ready, two pairs of Rosy Barbs were netted out of a 125g community tank kept at 74oF. One pair was put in each tank. It took them a few hours to settle down and start exploring the breeding basket. By the evening, the males were chasing the females and trying to lure them into the breeding baskets. One of the males was the dominant male in the community tank, and it was clear even after the pairs were separated into the 10g tanks which tank contained the dominant male. It chased its female much more aggressively, nudging her belly, and was much more brightly colored than the other male. The submissive male was in spawning colors, but much more subdued in both coloration and behavior. The fish were given a small meal of Repashy Soilent Green.

Day 2: Early in the morning when the sun was up, both pairs were engaged in spawning activity and appeared to be foraging for eggs among the marbles. At noon, both breeding baskets were pulled out and inspected for eggs. There were ~20-30 eggs in the basket from the tank with the brighter colored, more dominant male and none from the second tank. The eggs were transferred to an extra-large (6.6g capacity) Kritter Keeper outfitted with a gravel substrate, poret foam sponge filter, and a single large Indian Almond leaf that had been soaked in a bucket of infusoria-rich water. The initial water temperature was 74oF. A small heater designed for nanotanks with no temperature control was added. After several hours, the temperature came up to and stabilized at 77oF. The breeding baskets were rinsed and returned to the 10g tanks after an 80% water change with warm, 75oF water. The fish were given a small meal of Repashy Soilent Green.

Day 3: On 6/20/2019 the breeding baskets were pulled again and inspected mid-day. Like the previous day, the marbles/pebbles were removed and rinsed and the remaining water inspected. This time the basket from the tank with the dominant male had no eggs (perhaps the female had been exhausted of her eggs), but the second tank with the subordinate male did have a number of eggs. The water was poured out through a rotifer sieve to collect the eggs which were transferred to the same Kritter Keeper. Another large 80% water change was performed with 75oF water.

The males were switched to get eggs from alternate pairs to maximize genetic diversity. Once again, it took the fish a few hours to settle down in their new environment and get to know their new lady friends. And once again, the more dominant male got down to business chasing and pestering the female much more quickly and aggressively than the subordinate male. Plus, this time the males spent several hours chasing each other up and down the length of their respective tanks (they could easily see each other). A quick check late at night of the Kritter Keeper showed specks on the sides that seemed like they might have been larval fish. Not wanting to expose the larvae to bright light, I decided to leave them in peace and investigate in the morning.

Day 4: On 6/21/2019, a peek inside the Kritter Keeper confirmed a couple dozen newly hatched larvae clinging to the sides of the tank. This corresponded to 24-36 hours incubation time at 77oF. However, I was afraid that this was a bit too warm for the barb babies, so I switched nanoheaters with the neighboring Kritter Keeper where Blue Emperor Tetra eggs were being accumulated for hatching. The heater in the tetra tank was keeping the water somewhat cooler at 76oF. The appearance of larval fish prompted me to jump into action on the first foods front. First came a 50% water change of the bucket of infusoria (rotifers, paramecium, euglena, and Blepharisma) and a feeding of a handful of boiled wheat berries. The infusoria had been receiving regular feeding for two weeks in anticipation of a crop of fish larvae. The vinegar eel culture was also refreshed with a replacement of 25% of the volume with 1 part apple juice: 1 part water: 2 parts cider vinegar. The microworm cultures were also refreshed with Gerber multi-grain baby cereal to be ready when the fry became free-swimming. The vinegar eel culture is so productive that within 15 minutes of moving 500 ml into an Ehrlenmeyer flask for harvesting, the neck of the bottle was getting cloudy with nematodes. Big sigh of relief.

Next, attention turned to the breeding tanks. The tank temperature was down to 68oF in the early morning and the fish appeared somewhat sluggish. I suspected that while the fish had been productive at 70oF, a temperature of 68o was getting too low. At noon, the baskets were pulled and inspected. There were 5 eggs in one basket that didn’t appear to be fertilized, and no eggs in the other. There were three likely explanations for the lack of eggs: the females were spent having just laid eggs over the previous two days; the temperatures were too cold; or the fish had mastered the art of eating the eggs from among the marbles. I decided to address all three possibilities: first by giving a goodly portion of Repashy Soilent Green to each tank, second by putting in heaters set to 74o followed a couple of hours later by a 75% water change with 76o water; and third by cutting out black needle point mesh to lay over the top of the marbles to make it more difficult for the adults to dive into the marbles and suck out the eggs. Of course, by changing 3 parameters at once there’s no scientific basis for determining which root cause (or combination thereof) was responsible for the lack of egg production, but I wasn’t trying to publish a scientific study. I just wanted some more eggs from the current pairing of adult fish.

Day 5: On 6/22/2019, a few dozen eggs were transferred from the breeding basket in the tank with the dominant male. Less than a dozen eggs were transferred from the other tank. Both pairs of fish were fed well and another 75oF water change performed.

Day 6: On 6/23/2019, a few dozen eggs were transferred from the tank with the subordinate male to the Kritter Keeper. At this point I had 4 sets of eggs from the four pairings. This would yield as many Rosy Barb fry as I would be willing to raise so the adults went back into the 125g community tank.

Many dozens of larval fish started to appear in the Kritter Keeper. All the eggs had spawned within 4 days of each other, and the newly hatched larval fish were so small that predation of older fry on younger fry was not deemed to be a concern. All the eggs and larval fish were raised together.

Month 1: Probably somewhere in the range of 120 - 180 eggs hatched, but within 6 weeks or so it appeared that only about 80-100 fry were growing. For the first two weeks the larval fish were fed on biofilm (growing on a Catalpa leaf and some crepe myrtle bark), vinegar eels, and microworms. After that they were weaned onto infusoria. The fry appeared very healthy and robust. The disappeared had probably been outcompeted for food and starved, or else they were snacked on.

Month 2: The fry were still being kept in the Kritter Keeper which was getting over-crowded. However, I was travelling a lot and needed to transport the fry so they stayed in the Kritter Keeper and received daily water changes. They went to stay at Uncle Frank’s house for a week where they gorged on Daphnia.

At about 6 weeks of age, their diet was supplemented with Repashy Soilent Green. The abundance of rich food, between the daphnia and Repashy, caused a huge growth spurt in the fry with the littlest ones starting to catch up to the larger fry in size since there was less competition for food. At last they were moved into a 10g tank from the 6g XL Kritter Keeper. There are still 80-100 fry, so even the 10g tank was over-crowded and requiring water changes at least every other day. They’ll get moved again as soon as a 20g tank can be freed up.