Glowlight Tetra Care Guide: Tank, Feeding & Breeding

What are Glowlight Tetras?

Glowlight Tetras (Hemigrammus erythrozonus) is a small South American Tetra that has become a staple aquarium fish all around the world.

They are a translucent grey with a striking orange lateral line going down their side. They grow no more than 2” in length, but school in large groups hundreds strong.

Where are Glowlight Tetras from?

Glowlights originate from South America, in Guyana, where they are found in the Essequibo River, shoaling in huge schools, hundreds or even thousands strong.

As Guyana contains sprawling rainforests, the Essequibo river is very silty and tannic due to the abundance of muddy substrate and decaying plant material.

Glowlights today however, are mostly bred in farms and man made ponds where they are sold to wholesalers and fish stores, meaning the fish you see at your local fish store are likely captive bred.

Water parameters for Glowlight Tetras

As Glowlights are found in tannic water, they of course enjoy a slightly acidic pH and low hardness level, typical of many other fish from forested areas.

Feeding and diet of Glowlight Tetras

Glowlights, like many other Tetras, are omnivores. They like a mix of plant materials and algae, as well as protein rich invertebrates. 

Due to their small frame however, they lean more towards carnivory and their main diet consists of the tiny larvae of small flies, tiny worms like nematodes and infusoria like cyclops.

In captivity, Glowlights will feed on almost everything, flakes, small pellets, frozen and live bloodworms, daphnia, brine shrimp, algae wafers and so on. They are not difficult to feed by any means, and are usually the first to get at food.

Best tank mates for Glowlight Tetras

Glowlights are ideal community fish – they are peaceful, small, adaptable to a wide range of water parameters and are easy to feed. Due to their small size however, they need to be housed with other small peaceful fish that will not be able to swallow them.

This list contains our recommendations for the best fish to house with Glowlight Tetras:

Guppies

Guppies are another small, peaceful fish and make ideal tankmates for Glowlights. They are adaptable, will take the same food and will eat from all levels of the tank, picking up any food that slips past the Glowlights.

Guppies are also great algae control and have nice contrasting bright colours to go with any peaceful community tank.

Guppies do however, need to live in hard water, so a balance is needed to keep both fish healthy. If you want to keep these two fish species together, keep the pH close to neutral, anywhere from 7.0 – 7.5 and keep a low to moderate hardness level.

Other Tetras

Tetras are great as they can be mixed with other species of Tetras easily. Most of them like similar water conditions, take the same food and have similar temperaments.

They come in all different colours, shapes and sizes and look great together. They will however, not intermingle, and you can’t have 2 Lemon Tetras, 2 Black Skirt Tetras and 2 Glowlight Tetras and expect them to school together.

Fish will not interact the same with other species and instead you should be looking at something like 6 Lemon Tetras and 6 Glowlight Tetras, so that they can school with their own species properly.

Here are some other Tetra species that go well with Glowlights, just be sure that when you purchase them, you pick out fish from a healthy tank as disease can spread among Tetras easily:

• Neon Tetra
• Lemon Tetra
• Black Phantom Tetra
• Red Eye Tetra
• Emperor Tetra
• Black Neon Tetra
  

Cherry Shrimp

Due to the fact that Glowlight Tetras are very small, they can be housed with shrimp easily.  Adult Cherry Shrimp are large enough to not be eaten, and will live harmoniously with Glowlights.

Although Glowlight Tetras can and will eat baby shrimp, they are not active hunters like many of the micro predators out there, and as long as you have enough cover, many of them will survive and thrive.

Shrimp are ideal as they clean up any uneaten food that the Tetras leave behind, helping with filtration and maintaining a healthy ecosystem. Shrimp are a great cleanup crew!

Shrimps however, need calcium to be present in the water, so that their shells do not dissolve.  To add calcium, you can use crushed coral to provide a low to moderate level of carbonate hardness for the shrimp to absorb.

Corydoras

Any species of Cory Cat will go well with Glowlight Tetras. They are peaceful and non predatory, like similar water parameters and inhabit the bottom level of the tank, feeding on any food that gets left behind.

Corydoras are great community fish, but you need to keep them in a school of at least 6 or more, so it is best to do this in a 20 gallon tank.

How to breed Glowlight Tetras

Glowlight Tetras are bred in huge amounts in fish farms where they are kept in large ponds. It is possible to breed them in an aquarium too, although you need to set up the right conditions for this to be possible.

To condition Glowlights, they need to have their environment setup similar to their native habitat in Guyana – this means having tannic or “Black Water” which is soft and acidic.

To achieve this, it is best to use driftwood, dead Catappa leaves or oak leaves, peat moss or anything else that releases tannins. Maintain an acidic pH that lies anywhere from below 7.0 down to 5.5 and provide lots of plant cover and rockwork, or have spawning mops for them to drop their eggs onto.

Keep the lights dim and increase the temperature to around 27C – 28C (80F – 82F).

Feed them heavily with live foods such as daphnia and baby brine shrimp and disturb them very little so as to not cause stress. Conditioning them like this is the closest thing you can achieve to their natural habitat, so they feel compelled to breed as it simulates their breeding season.

However, for all of this to be a success, you will need a male and female.

How to sex Glowlight Tetras

Glowlights are sexually monomorphic so it can be hard to distinguish between sexes. For this reason, it is best to get a group of around 6 or more to ensure your chances of getting a good mix of male and female.

There are subtle differences between them, although they are mostly only visible when the fish mature and transition into breeding condition.

• Typically with Glowlights, the females are more rounded and plump than the males.

• Males are smaller and slender, with a more sleek body plan with a thinner peduncle and more pointed finnage.

Males will also be seen sparring with one another, so if you see this behaviour happening a lot, chances are your fish are males.

Rationing Glowlight Tetras

During mating, male Glowlights will compete for space and females, so it is best to house them with plenty of space and cover so that they can avoid each other.

Glowlights can be bred communally and a single pair spawning often triggers the surrounding fish to do the same. However, the males will spar and to avoid too much fighting, it is better to have more females than males, so that the competition is reduced.

A 1:3 ratio is best to give males enough to compete for, or they can be housed in single pairs or as a harem. Whatever situation, typically, less males and more females is best.

Glowlight Tetra spawning and fry

Glowlights, like most Tetras, do not parent their young, and once the eggs have been laid, their parenting duties are over and it is time for you to step in.

Once your fish have spawned and stuck their eggs to the mops or plants, separate the parents by moving the adults or the eggs to a different tank.

Then allow the eggs to hatch, this will take around a day or so; but, during the egg stage, they are at risk of fungusing, so it is important to keep the pH low and maintain clean water quality.

Tannins will also help deter fungus, or you can use methylene blue to prevent it, although this will have to be removed over the next few days. Once the eggs hatch they will emerge as wigglers, unable to swim, they will glue themselves to a surface while they absorb their yolk sack for the next 3 days.

After 3 days are up, they will develop into free swimming fry and are to be fed infusoria 3 times a day, and eventually moved onto live baby brine shrimp, daphnia and crushed flakes.

Depending on  the temperature, quality of water and amount of food they are given, they will take anywhere from 7 months to a year before they mature.

What tank size do Glowlight Tetras need?

Glowlights can be housed in something as small as a 10 gallon tank, due to the fact they themselves are very small and are non aggressive.

However, a 10 gallon only allows you to keep a small group of around 5 fish, which is okay, but if you want your Glowlights to truly thrive, they need to be housed in larger numbers, in a larger space.

We recommend keeping them in a 2ft tank, of around 125 litres. 

This allows you to keep a larger school of them, and allows them to feel more comfortable in their captive environment.

What plants are best for Glowlight Tetras?

Like most other Tetra species, they are great for planted tanks and really appreciate lots of foliage in the tank.

Since Tetras mostly swim around the mid level of the tank, the best plants are those which produce tall stems or leaves which the tetras can swim through and hide in. Here are some recommendations:

• Amazon Sword
• Jungle Val
• Java Fern
• Bacopa caroliniana
• Elodea densa

Tips and tricks for Glowlight Tetra care

As mentioned, Glowlights in the wild like to be in huge schools. Housing just 2 of them in your tank is not going to give them the social requirements they need and they may often bicker between themselves, or become highly stressed.

If you want to keep them successfully, and see them swimming confidently, then you need to have at least 6 of them in your tank. This gives them the comfort and safety they need, as they have evolved to want to stay in large groups to ensure their safety and survival.

You may not think so, but fish are highly social creatures and can become stressed and depressed when housed on their own, so get yourself a group of Glowlight Tetras, not just 1 or 2.