Moenkhausia pittieri (Diamond Tetra) Spawning Report
Submitted by Patchin Crandall Curtis
Background: The diamond tetra is found in shallow, vegetated parts of Lake Valencia, as well as in several slow-moving tributaries. Lake Valencia and its watershed is situated between two picturesque mountain ranges in Venezuela. Lake temperatures are tropical varying from 75o – 82oF. The lake surface is at an altitude of 410 m (1,350 ft), the maximum depth is 39 m, and the mean depth 18 m. The lake has a number of small islands, some inhabited. Lake Valencia suffers from algal blooms caused by continual influx of untreated wastewater from the surrounding urban, agricultural, and industrial land uses. This contributes to ongoing eutrophication, contamination, and salinization of the lake negatively impacting this gorgeous community fish.
Colony: Purchased pond-raised males from Matt Chambers on 1/6/2018 and wild-caught females from the Wet Spot on 4/17/2019. The current colony consists of 5 males and 3 females. They are kept at 76oF. I have experienced losses when water temperatures were consistently higher than 78oF and thus believe that they enjoy better health when maintained at the lower end of their reported temperature range.
The wild-caught females were juveniles when the fish arrived in April. They were grown out on a diet of Repashy Igapo Explorer and Soilent Green, and New Life Spectrum, Cobalt, and North Fin brand community pellets. At least twice a week they were fed a variety of frozen foods. When a single fry somehow survived in a community tank with other tetras, I decided it was time to undertake some controlled spawning experiments.
Tank Set-Up & Spawning: On 9/15/2019 a 20L tank was prepared with a coarse gravel bottom to catch eggs (CaribSea Joe’s Creek), 2 pieces of Malaysian driftwood with Christmas moss attached with black silicone hairbands, and spawning mops dangling down in the corners suspended from Styrofoam floats to simulate the overhang from vegetation at water’s edge. A 50% water change was performed with 50/50 tap water/RO mix. Flourish fertilizer was added to help establish the java moss, and Tetra Black Water Extract was added to stain the water and provide tannins. Water temperature was set at 77oF. In the evening, the fish were netted out of the community tank and placed in the 20L. The next morning, a catalpa leaf and an alder cone were added to the tank along with a disk of Repashy Igapo Explorer. The lights were turned off and the fish took refuge in the darkened corners of the tank underneath the spawning mops where they remained hidden and inactive. After waiting 15 minutes, I turned off the air supply thereby cutting off the current. The fish then moved into the center of the tank and started to swim around to investigate their surroundings but after 2 hours became inactive again, so I turned the air back on adjusting the flow to be moderately slow. They perked back up again, with males lazily circling each other but no overt spawning behavior. After a few days of heavy feeding, the males appeared to display to each other but I never saw a direct spawn with a female.
On 10/1/2019 the Diamond Tetras were removed to repurpose the tank for quarantining Croaking Gouramis for the Spring All-Day Auction, and then some newly purchased Sharp-Nosed Chocolate Gouramis. The tank was thoroughly siphoned and cleaned a couple of times between fish shipments. At this point, my working assumption was that any eggs deposited by the Diamond Tetras had probably been either eaten or siphoned out, or the fry eaten by the Gouramis.
Raising Fry: Then, on 10/18/2019 after feeding the Chocolate Gouramis heavily on newly hatched BBS, I noticed a bunch of relatively large, plain, silver fry with full guts that looked near to bursting. The first day I could just see 6 or so, the next day 8, and then 12 the next. They hide very effectively in the floating plants and among the driftwood and java moss. They are already quite large ranging from 5 mm to 1 cm in length. Their maximum possible age is 5 weeks old, so the fry must be very fast-growing compared to Blue Emperor Tetras which would take at least 12 weeks to reach a similar size.
On 11/1/2019 the tank was thoroughly cleaned and the fry placed in a clear container to be photographed. The fry are somewhere in the range of 4-6 weeks. They may be from a single spawn or multiple spawns sometime during the last 2 weeks of September.