Spawning Report: Tanichthys micagemmae (Vietnamese White Clouds)

Tanichthys micagemmae (Vietnamese White Cloud or Vietnamese Minnow) Spawning Report

Submitted by Patchin Crandall Curtis

The fish was only described in 2001, and has only been in the hobby for a relatively short time. The Latin species name means sparkling gem, and so they are. This species hails from the Ben Hai river system which flows through north central Vietnam and not from the White Cloud Mountains in China like its congener, Tanichthys albonubes. So, the common name is a bit of a misnomer but it does call attention to the similarity in appearance of these two fish. Phylogenetic studies suggest that T. micagemmae is the parent species, and T. albonubes a younger relative (Fang. et al., 2009: Molecular phylogenetic interrelationships of the south Asian cyprinid genera Danio, Devario and Microrasbora (Teleostei, Cyprinidae, Danioninae), Zoologica Scripta 38(1): 1-20).

The type locality is a clear stream flowing over sand. Water parameters were not measured at the collection site, but they are thought to thrive in cooler temperatures, 65-74o F although some reports say they prefer warmer temperatures than T. albonubes.

Despite a full-grown size of only 1”, this is a bold and lively fish that likes a bit of current and swims out in the open. No cowering behind the rocks for these little beauties. They like to show off and see what’s going on in the fishroom. At least this is the way they are behaving in a small, species-only tank with plenty of open space. Some reports of this fish describe them as shy, but that has not been my experience.

They are bold eaters and quickly learn who feeds them. Despite every description of this fish saying that they readily accept all food, I haven’t been able to coax these wild-caught fish into eating prepared food yet. They love frozen cyclops, daphnia, and rotifers which they gobble up, but I can’t get them interested in Repashy, Sera stick-on disks, or any sort of micro-pellets (Cobalt, North Fin, New Life Spectrum). They only eat from the surface and water column. Once food hits the bottom, they won’t touch it or show any interest in it. This is unlike most of the cyprinid species I’m keeping right now which graze all day long on anything and everything.

Tank Parameters

Breeding colony: 8 wild-caught fish purchased from The Wet Spot on 4/17/2019. The males and females of this species are somewhat distinguishable: the females are rounder when gravid, and the males have flashier finnage with more yellow markings. There are at least 3 males and 3 females, but it’s hard to say if the other 2 are females or subordinate males.

Tank: 15g cube tank

Hardscape: Fluval plant substrate, gray Seriyu stone hardscape

Plants: sparsely planted with small Cryptocoryne sp.

Filtration and Water Flow: Custom mattenfilter housed in 3 back compartments separated from main tank by a plastic grate. Water flow is fairly strong. Young fry hanging out at the surface are swept into the back compartments where they grow without excessive interference from the adults.

Temperature: Unheated water ranges from 68 – 71oF

Water Quality: Soft, neutral water, 35% changed every other week

Spawning

On June 19, 2019 there was what appeared to be a cloud of sparkling chips of sapphire and emerald at the surface in the back of the tank out of the direct current. The fry were so small I couldn’t really see them, but they were like brilliant specks of green and blue. Not expecting nor being prepared for this spawn, I had no other tank into which to move the fry. I thought I remembered reading somewhere that this species would voraciously eat their eggs but that they would generally leave the fry alone as long as the adults were well-fed. Now I can’t find this reference.

I immediately started feeding the fry vinegar eels since they required something extremely small that would stay at the surface. I added the vinegar eels using a pipette to make sure there was a cloud of nematodes exactly where the fry were located. They were definitely large enough to eat the nematodes because the second the vinegar eels were added, slivers of blue and green started darting all over the place. Many adult fish won’t bother with such microscopic live food, but not T. micagemmae. The adults immediately got in on the action as well, and I was concerned that I was drawing the attention of the adults to the cloud of fry, and that all the fry would be eaten. It’s been one week now since the fry appeared, and as far as I can tell, more or less all the fry are still there so it seems as though the adults aren’t predating them.

Month 1: It took about 4 days before the fry were big enough to actually see with reading glasses. At one week of age, they look like fry. They grow fairly rapidly and reach nearly adult length in 8 weeks. I had to travel in July. Since the fish weren’t going to be fed while I was gone for a week, I removed as many of the smaller fry from the tank as I could, and placed them in a 6g XL Kritter Keeper and brought them with me to Tennessee where they could get regular water changes and feedings of live food 2-3 times per day. Then, they went to stay at Frank Cowherd’s house for over a week where they were treated to Daphnia magna. The fry were far too small to eat the adult Daphnia but their growth rate suggests that there were plenty of baby Daphnia for the fry to eat. Most of the fry that were left in the main tank survived. There are about 8 of those. Only 6 of the fry that were transported survived. I believe I lost most of them travelling back from TN. The water temperature climbed to 76oF which seems to be too warm for these fish.

Month 2: All 14 fry are putting on good growth eating a mix of live and frozen food. They show no interest in eating Repashy. They only feed from the surface and the upper part of the water column. They will eat the smaller size fractions of Golden Pearls. Their length is nearly that of adults, but they still have a lot of body mass to attain at 8 weeks of age.

Month 3: The fry are nearly full-length but will still put on another 30% or so of body weight as they fill out a bit more. They are not yet sexually mature. Like their wild-caught parents, the fry are resistant to taking dry food. They will eat some Golden Pearls (200-300 and 300-500 mm size fractions) but greatly prefer frozen cyclops and blood worms and any live food. They refuse most dry food and still show no sign of interest in eating Repashy foods.