Glowlight Tetra Feeding: Diet, Live Foods, and How Often to Feed

A glowlight tetra is about 1.6 inches (4 cm) long and will take nearly anything small enough to swallow. That makes feeding simple, and it also means the keeper, not the fish, has to set the limit on how much goes in.

Feeding Schedule by Life Stage

Glowlight fry wait out their yolk sacs before eating anything, juveniles take several small meals, and adults need only one or two light ones.

Glowlights scatter their eggs, and the parents will eat them if left in the tank, so fry are raised apart from the adults. The eggs hatch in 24 to 36 hours, and the fry then live on their yolk sacs for several days before they need feeding. Infusoria is the usual first food, though glowlight fry have occasionally taken brine shrimp nauplii as soon as they swim free.

For adults, the portion is what the school clears while it is still feeding hard. If flakes or pellets reach the substrate untouched, the next pinch is smaller. Watching also shows whether every fish is getting a share. Uneaten food rots into ammonia, the waste that the nitrogen cycle in a mature tank has to keep clearing, and a quick drop in water quality is how an easy eater ends up in a fouled tank.

What Glowlights Eat, in the Wild and in the Tank

Wild glowlights are omnivores. Their diet is worms, small crustaceans and plant material, which is the reason a mix of foods suits them better than a single product. The captive menu follows from that: a dried staple, with small live and frozen prey added around it.

Build the daily diet on a quality dried food of a suitable size. A slow-sinking micro pellet or a small flake does the job, and either one is eaten readily by a school this size.

Small live and frozen foods are the best way to widen the diet. Bloodworm, daphnia and brine shrimp are the usual choices, and freshly hatched baby brine shrimp make an occasional treat. Offer them as part of the regular rotation instead of the whole meal, so the dried staple still carries the day-to-day nutrition. They are also what brings a glowlight to its best condition and color.

Daphnia brings a risk the dried staple does not: it and cyclops are common intermediate hosts of Camallanus, a parasitic worm that reaches the fish through the food.

Dried food loses its value once it is opened. A container kept at room temperature is thrown out 2 months after opening, and one stored in the freezer after 6 months. Frozen bloodworm and brine shrimp keep for a year, and once thawed they are never refrozen.

Foods to Avoid

• Live tubifex. Tubificid worms are the host of the parasite behind whirling disease, and keeping fish away from them is how that disease is prevented.
• Freeze-dried tubifex as a regular food. It is sold as an occasional treat for glowlights, and freeze-drying is not known to remove the parasite risk the live worms carry.
• Flake sized for bigger fish. It can be too large for a small mouth to take easily, and pieces a glowlight cannot get down sink and rot.
• Rich, fatty or starchy diets. Fatty liver disease is a common problem in captive fish, and diets high in carbohydrate or fat, and rancid food, are among its causes.

Why Glowlights Stop Eating

1. Bolder tankmates. In a mixed tank, check that faster or pushier fish are not taking most of each feeding. Companions that pass the compatibility checks for sharing a tank keep feeding time fair for a fish this size.
2. Too small a school. Glowlights kept in small or lonely groups spend most of their time in hiding, away from the food.
3. Internal parasites. Spironucleus, an intestinal flagellate, causes weight loss and a lost appetite.

When to Worry

Body shape in a glowlight depends on sex. Females are more rounded in the belly, and a female in breeding condition looks very full, so a plump female is not overfed. Males are slimmer, with a slightly sunken belly region, so a lean male is not a hungry one. The signs that need action:

• One fish thinning while the rest eat. That fits an internal parasite, one of the glowlight tetra health problems that needs a diagnosis before any medication goes in.
• A red thread at the vent. Camallanus shows as red worms protruding from the vent, most likely in a tank fed live cyclops or daphnia.

When You Go Away

While you are away, the fish need either a person to feed them or an automatic feeder, and an easy eater like this one makes overfeeding the risk with both.

For a sitter, measure each meal out ahead of time, for example into a labeled pill organizer with one compartment per feeding, so nothing extra goes in. Show them once, and leave your number.

For an automatic feeder, set it up and test it for several days before you go, with a food it dispenses well, checking that it is not jamming or overfeeding.

An adult glowlight asks little more than that: a small dried food, a rotation of live and frozen extras, and a keeper who stops before the water suffers.

Sources & Further Reading