5 min read

The Glo-Light Danio

Written by Russell McAndrews

Apparently named incorrectly Danio choprae, Hora, 1928 is currently being gender corrected to C. choprai.

Even without glasses, I could tell that I had never seen this fish before a Danio that looks like a Glowlight tetra.  Once I donned my glasses, the fish was revealed to be exquisite.  But it wasn’t until I happened to expose the group of them to sunlight that the total splendor became apparent.  On top of everything else, the males took on a golden-yellow whole-body glow.

I consider myself fortunate to have picked these animals up at a club auction in Norwalk, CT.  Now I had to go home and find them a home.  I’ve kept Danios before but never set up a “Danio” tank.  My eight D. choprae were juveniles or young adults.  Circumstances being what they were the fish went into a 30L with some very small cichlid fry.  The group settled in and appeared happy.  (Yes, I’m convinced that fish have emotions!)  They grew a little and fattened a little but no obvious sexual differences manifested themselves.  Part of the trouble was that I don’t see as well as I used to.  Part of the problem was that these fish are very small, full grown at 1.25 - 1.5 inch total length.  The remaining part would turn out to be that sunlight I mentioned earlier.  Once the males changed color and lit up it seemed much more apparent that the females were not just less colorful, but considerably fatter than their counterparts.

Soon I began to see spawning type behavior, namely male sparring.  Operating under the assumption that they must be maturing if not already mature, I took my good friend Jim Carmark’s advice.  I set up a small “cook-book” tank for spawning zebra danios, i.e. a small tank with shallow water and marbles on the bottom.  After two days I returned the two females and one male to the main colony.  Three days later I noticed tiny glass slivers amassing near the surface.  It had worked!  I had trouble believing that it could be that simple and, of course, it wasn’t.

What was I going to feed them?

These fry are SMALL.  While I can’t give you exact numbers, I would estimate that they are similar in size to Betta or Gourami fry.  I didn’t have an infusoria culture.  I was unprepared.  Still I was hopeful.  Elsewhere in my fish room I recently discovered Giant  danio fry in a 30L with ten adults and five cichlids ( C. nanoluteus ).  They must have survived on crumbs of flake food that I fed the tank, or single-celled organisms within the tank.  Later, after the babies became large enough to be noticed a friend gave me some micro pellets in the 50micron range, so I was hopeful.  At one week old the fry are still unable to eat baby brine shrimp, I tried.  They do however seem to be interested in powderized flake food that I’ve been offering along side the “micro pearls”.  I wonder now if this might not reflect a preference for feeding from the surface for the water?

It seemed a wee bit strange that I had never seen this fish or a picture of it before.  I’ve been very active in the aquarium trade and hobby since 1969 and  this is a beautiful, small animal seemingly perfect for the aquarium trade.  My son who recently returned to Australia informs me that it is common there, even showing up in amongst feeder platies.  Some more research was called for.

Endemic to Myanmar, the “glo-light” danio’s common name is meant to indicate the fish’s similarity to the tetra of the same name, as opposed to the “glo-fish” which is coincidentally a danio which has been genetically altered by man.  These transgenic zebra danios are enhanced with jellyfish, or starfish genes for bioluminescence.  D. choprai only gets to 1-1.5 inches (2.5-3cm).  It seems to be part of a complex which is poorly understood.  Most of these animals appear to be closely related, whether or not they will turn out to be the same species or several time will tell.

I made other attempts to repeat this success but they didn’t work!  First I used 2 inches of new water in a 10 gallon tank.  Marbles covered most of the bottom and java moss was available to deposit their eggs.  This time however, I moved the entire group of eight adults instead of just three.  After three days they were shuffled back to their 30 gallon long home.  I waited and watched.  Two days went by, three and them four, after five I gave up - no fry had been generated.

Meanwhile in the 30 long where I house 10 adult giant danios tiny fry of several sized are appearing.  There appear to be four distinct spawning events that each produced at least some progeny.  Unfortunately, the fry have stopped showing up.  I believe the cause is sibling predation.  The baby danios seem to be the first ones to notice the eggs and newly hatched siblings.  If they can eat them they do.  If my theory is right I should see a new pulse of survivors when the first batch becomes too large to notice the new arrivals.  Having just found babies in with the parent D.choprai.  I’m curious to see if these babies prey on one another.

Just now, while writing this I’ve noticed fry in the parent’s tank.  There are only two of them but success none the less.  They seem to be younger than my two-week old batch but I would imagine them to grow more quickly in the larger tank.

I’m watching the parents spawn right now.  One male in especially dark dress keep traveling from the school hovering above down along the bushy plants to the bottom.  He’s swimming in a fluttering way as to attract females.  His method reminds me of male mouth brooding cichlid attracting a mate.  On the bare glass tank bottom there are hair moss and other algae.  One at a time, the females accompany the flashy male to the bottom.  They roam around near the bottom and through the plants presumable dropping the fertilizing eggs along the way.  In the school above, the other male seemed to act agitated snapping at the females and each other in passing.  I’m a little surprised that they are spawning more on the bottom greenery than the potted Cabomba, but I guess that was a bad assumption on my part.

Attempt number 3 is a 10 gallon tank full of aged water at the same temperature.  This time I’m only moving the bottom greenery which I just witnessed them spawning in maybe when I move this greenery in to the first spawning tank I unknowingly moved eggs.  Maybe they never spawned in the spawning tank.  It seems to me, at the risk of anthropomorphizing, that being suddenly netted and moved to a totally strange tank would ruin the mood.  People have assured me that these fish spawn on instinct not mood, however I remain unconvinced.  I noticed fishes exhibiting emotion in my fish room on a number of occasions as is evidenced by moods.  Anyone who has seen a pissed off female cichlid knows what I mean.  Who can say whether an animal’s flight is instinctual or just fear, or maybe a little bit of both.

Success!  On day 5 I gave up, resigned to another failure.  A day passed while I tried to imagine what had gone wrong.  On day 6, success!  The first sliver appeared to me then another.