Glowlight Tetras Are Never Handled, So the Trip Home and the Tankmates Matter

A glowlight tetra (Hemigrammus erythrozonus) is a lively, peaceful fish marked with a red stripe along each side, and an adult measures about 1.6 inches (4 cm). Nobody picks one up. The hands-on part of keeping it comes down to a net, a bag and the time it takes to move from shop water into tank water. After that, the choices that shape its life are the size of the school and which fish share the tank.

How Many to Bring Home

Six is the floor, and ten or more is the number to buy. Glowlights shoal by nature and fare much better among their own kind, and a school of 10 fills the middle of the tank with movement and color, working lower toward the floor as it grows.

That school needs a tank with a base of 24 x 15 inches (60 x 38 cm), roughly 18 to 20 gallons, a footprint that beats the 10 gallons sometimes sold for the species. Ten fish arriving together add a sudden load of waste, so they belong in a tank that has finished its nitrogen cycle and has been running since.

Netting: One Net per Tank

A net is the only thing that touches a glowlight, and the transfer goes most smoothly with the bag already in the water. Float a partly filled bag at the surface, open it there, and net the fish across into it. A helper holding a half-full bag up in the air while fish get tipped in from the net is the version to avoid.

The net belongs to one tank. Nets, siphon hoses and other gear that have not been disinfected should never pass between tanks, because they can carry ich from one tank to the next. A quarantine tank gets its own net, and so does the display.

The Drive Home

A journey of more than a short drive calls for the oxygen and insulation planning in moving fish over a longer trip.

Acclimation: Float, Drip or Straight In

Wild glowlights come from soft, acidic water, and the tank should run at pH 5.5 to 7.5 and 2 to 15 dGH. Testing the tank's pH and hardness beforehand shows how far apart the shop's water and the home tank sit, and that decides the method.

The floating routine:

1. Turn the lights off. New arrivals stay in the dark for the whole process, never under a bright tank lamp.
2. Mix the water gradually. Roll the top of the bag down and add a little tank water every few minutes, until the bag holds mostly aquarium water.
3. Net the fish across. Lift them out and release them into the tank, and discard what is left in the bag. It carries waste from the trip and can carry pest snail eggs.
4. Count, then give them quiet. Check the bag, net and floor for a fish left behind. An hour or two with the lights still off lets the school settle.

Do not expect the first meal on day one. New arrivals often take a day or two to start feeding; offer a little food and remove what is ignored. If they are still refusing after that, the fix is a different food, not more of the same.

Quarantine is the single most important step for every fish added, and most of all for fish bought online. New arrivals spend at least 30 days in quarantine before they join an established tank.

Temperament: Lively and Peaceful

Glowlights are active, colorful and peaceful, with aggression rarely a concern. They use the open water in the center of the tank, with larger shoals sitting low, which makes a school of them a natural fit for a calm community.

Tankmates That Work

The test is a peaceful fish of similar size that cannot swallow a 1.6-inch tetra. Good matches include:

• Livebearers such as guppies and mollies.
• Danios, rasboras, cherry barbs and other peaceful tetras.
• Bottom dwellers such as corydoras, kuhli loaches and clown loaches.
• Honey and sparkling gouramis.

Larger fish that see a small tetra as a meal are the ones to avoid. Angelfish are the standard example: a mature one will eat tankmates this size. Any candidate's adult size is worth checking before it goes in.

Telling Males From Females

Adults are easy to sex. Mature females are rounder through the belly and tend to grow a little larger than males, while males are slimmer, with a slightly sunken belly. A school of 10 needs no sorting, and the distinction matters only to a keeper planning to breed.

Fish Tank Granuloma: Gloves Over Cuts

Floating the bag, netting the school across and every bit of tank care afterward put a keeper's hands into aquarium water, where Mycobacterium marinum can live. The bacterium is found in fresh and salt water and in home aquariums, and a cut or scrape is its way in, which puts people who keep fish at higher risk.

A reddish to purple bump is the usual first sign, typically 2 to 3 weeks after exposure, and it slowly turns into a painful nodule that may break open into a sore. Fingers, elbows and the backs of the hands are where it most often appears. Treatment can run for several months on more than one antibiotic, so a lump that does not go away needs a doctor, told about the tank.

Prevention is simple: rubber gloves for any job in the water, a hand with a fresh cut kept out of it, and the hands and arms washed thoroughly when the work is done.

First-Timer Mistakes

• Buying three or four. Six is the floor and ten the goal.
• Stocking an uncycled tank. Ten fish arrive with ten fishes' waste.
• Sharing one net between tanks. Each tank keeps its own.
• Pouring the bag in. Net the fish and tip the water away.
• Slow-mixing a shipped order. Temperature first, then straight in or a detoxifier.
• Skipping quarantine. Thirty days, above all for fish bought online.
• Adding an angelfish. A grown one eats glowlights.
• Bare hands over a cut. Gloves first.

A school of ten glowlights that came home in a dark bag, crossed on its own net and settled in a quiet, dim tank has had the only handling this fish ever needs, and from there its welfare rests on the company it keeps.

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Sources & Further Reading