Some aquarium fish will drift in and out of fashion, but the Glowlight tetra never seems to go out of style. John Rundle explains how he breeds these lovely community fish.
In my many years of fishkeeping there have been a lot of changes in the popularity polls of species. I suppose in some ways it’s akin to clothes that come into fashion then fade away, perhaps to dramatically return at a later date.
Our fish also go through these phases, with new species coming into vogue only to rapidly become yesterday’s choice. However, one group is always found in the dealers’ tanks — the 'bread and butter' stock. It incorporates the fish that seem to have been around for ever and bred in vast numbers by the fish farmers.
Unsurprisingly all are easy to keep, but one species, the Glowlight tetra, has everything going for it. It’s excellent for the community aquarium, perfect for the newcomer to the hobby, tolerant of varying water conditions and attractive. It’s also an ideal challenge for the first-time breeder.
The species name of Hemigramus erythrozonus means 'with a red zone or stripe'. Since it was first exported from Guyana to Europe in the 1930s it has certainly played the 'change the name game' to the full.
J H P Brymer identified the species on the advice of Dr E Trewevas. The tentative identification was Hyphessobrycon gracilis (Reinhardt) but this was not accepted because Reinhardt’s material was from a different locality. It was also of a different build and coloration — more allied to the Flag tetra (H. heterohabdus).
The obvious red glowlight stripe runs the full length of the fish’s body, with a basic background of olive to yellow-green. There are silver areas in the belly region and the dorsal and tail can show white tips. Adults
grow to around 4cm/1.6” in length.
Telling the difference
Adults can be easily sexed, with the males being slimmer and having a slightly sunken belly region.
The females are larger and fuller in the body, but there are no noticeable colour differences between the genders.
Fancy trying to breed them?
These fish make a great first-time breeding project and here’s how I do it.
I use a 38 x 18 x 30cm/15 x 7 x 12" tank, but any size up to 60cm/24" will be fine. It must be well cleaned beforehand and I use cooking salt as a disinfectant to clean mine.
The breeding tank will be bare, having no gravel substrate. A small sponge-type filter is always fitted and the temperature set to between 25-26°C/77-79°F.
This fish tolerates varying types of water and will do well in tanks in differing regions all over the country. However, when breeding, try not to exceed pH 7.2 and DH of 6.5. I’m sure Glowlights will breed above these readings, but fewer eggs will be produced.
In my case the water comes out of the tap at pH 6.5 to 7 and is very soft, making it very easy to breed these tetras.
Next I place spawning medium in the breeding tank. I use mops made from nylon wool cleaned in very hot water.
Newcomers to breeding often place too many mops in the tank and the fish will just hide in the mass. I place a couple on the floor and suspend one on a strip of polystyrene over the sunken ones.
The tank is now ready for the intended breeding pair.
Having reached this stage I need to know I have a pair that’s actually ready to breed. Very often females not in breeding condition are used and no eggs are produced. There should be no doubt when the Glowlight female is in condition as she will be very robust in the belly.
As is normal when breeding egglayers of this type I place the selected pair in the tank in the evening and cover it with newspaper to keep out bright light. When I was in Singapore visiting fish farms the tetra breeding tanks were kept dark for the fish to spawn, so I adopted this method every time since.
Tetra species can lay light-sensitive eggs, so that’s why the tanks are covered.
Watching the Glowlight spawn is a sight to behold. The male will drive the female over the mops where the pair appear to quickly lock fins, embrace and perform a barrel roll while the eggs are extruded and fertilised. This action is repeated until the female releases all her eggs, which are slightly adhesive.
More than 200 eggs can be laid by an adult pair. Once these clear eggs can be seen and the female is showing signs of being slim again, the pair can be removed. Parents will eat the eggs if left in.
I keep the tank covered until the eggs hatch and are free swimming. Within 24 hours the eggs will hatch and if you lift the mops you’ll see the fry wriggling.
The fry will feed on their yolk sac for about five days, so do not feed yet. After this time they will become free swimming.
The fry now need an external food supply. I use my own cultured infusoria, but Glowlights have occasionally taken brineshrimp nauplii when first free swimming.
Change about 25% of the tank water once a week, taking care not to remove the fry.
Glowlights can produce large broods. Numbers may reduce from the first free swimmers, but on average a good-sized brood could be around 100 fish.
Growth rate is constant and when about 3-4mm/0.12-0.16" the fry will need a larger home. At this time they are able to take crushed dry food and I feed them live foods such as Grindalworm.
Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.