Rainbow Darters (Etheostoma Caeruleum)

rainbow darters

Rainbow darters (Etheostoma caeruleum) are small fish that live in the Midwest, including Wisconsin and Illinois, and parts of the East Coast, including New York and Vermont. Although darters come in a variety of colors and can be difficult to identify, it’s much easier to distinguish between two different types of rainbow darters if you know what characteristics to look for. Identifying your rainbow darter’s species will help you care for them more effectively while they’re in your aquarium or pond.

Six native darter species live in North America, the most common of which is the rainbow darter. These colorful fish have been widely introduced into other regions, and as of 2012, had been found in Europe, Asia, Africa, and South America. Etheostoma caeruleum comes in several colors depending on their habitat and location, but the most common colors are blue-gray with red or orange spots or blue-black with yellow markings. These fish typically measure between 2 to 3 inches long, with males growing larger than females.

Origin and descriptions

Rainbow darters are native to the central and eastern parts of North America, ranging from Canada in the north to Mexico in the south. This species spends most of its time hiding under submerged rocks and logs, although it can sometimes be found swimming in shallow water in creeks and small rivers. Rainbow darters feed on tiny invertebrates, such as water fleas, small insects, and other aquatic organisms. They use their specialized mouths to suck in their prey, which they then swallow whole.

Species profile

rainbow darters

The rainbow darters belong to the family Percidae and are a small species of fish. They can be identified by their bright colors, with males displaying brighter colors than females. Males typically have blue and red scales on their sides, while females have more yellow or green scales.  Rainbow darters are one of only three darter species that live in cold water habitats, which is why they’re sometimes referred to as coldwater darters.

These fish live in fast-moving rivers and streams where they feed on insect larvae and other invertebrates. They can grow up to 3 inches long but usually stay around 2 inches long as adults. They’re found across Canada, Alaska, the northern United States, and parts of Europe.

Rainbow darters scientific name

The scientific name of the rainbow darter fish is Etheostoma caeruleum

Habitat

Rainbow darters like ponds and small streams that are near a larger body of water. While they can be found in freshwater, they’re actually more common in brackish waters. They live at a depth of roughly one foot to 20 feet but prefer their home to be between four inches and two feet deep. Rainbow darters avoid moving too far from their homes, as they’re poor swimmers and don’t fare well in open water.

A healthy population of rainbow darters should have an abundance of plants within its habitat, as these fish rely on them for shelter and food. In addition to plants, rainbow darters require rocks or other hard surfaces with crevices for hiding spots. When it comes to time , male rainbow darters will build nests out of gravel or sand on top of rocks or other hard surfaces; females then deposit eggs into these nests.

Rainbow darters size

Rainbow darters are small relatives of walleye. They can grow to a size of 2-3 inches (5-8 cm) in length.

Rainbow darter aquarium size

Due to the small size, the minimum recommended tank size for rainbow darters is 10 gallons (38 liters).

Tank requirements

Rainbow darters require some special attention when setting up their tank. They prefer a tank with thick vegetation. Keeping them in low-visibility water makes it harder for predators to spot them and attack them. A heavily planted aquarium with a mister is also recommended for these fish due to their tendency to jump from their environment if startled.

Since they are air breathers, a sponge filter is preferred over an under-gravel filter, as well as frequent water changes of 10% every week or two. The tank should be at least 10 gallons, but preferably more.

These fish can live alone or in pairs, but adding more than two males will result in fighting over territory. This species of darter tends to be very aggressive towards other types of fish that are not closely related to it; therefore, only keep other Etheostoma species with it.

Tank mates

The rainbow darter is a community fish that can be kept with a wide variety of peaceful tank mates. While they are not aggressive, they do best in large tanks and can be territorial with members of their own species.

Some good tank mates include zebra danios, minnows, catfish, northern redbelly dace, mud minnows, native killifish, and loaches.

Breeding

rainbow darters

Rainbow darters usually begin breeding when they reach a length of about 1.5 inches and sometimes as early as some months old. This species is known to spawn in or near vegetation, such as lily pads, around one month after ice-out. This may occur between mid-April and mid-May depending on water temperature and weather conditions.

Courtship involves two males swimming side by side behind a female with each male trying to entice her to mate with him. Once she has selected a mate, she will lay eggs on submerged vegetation or gravel. The female will lay approximately 50 eggs at a time and then swim away leaving them to be fertilized by the male. He then guards them until they hatch some days later.

The fry remains protected under their father’s watchful eye for another week before venturing out into open water where they become independent from their parents.

Are they aggressive or peaceful?

Etheostoma caeruleum, rainbow darters, is peaceful and should be kept with other peaceful fish. Do not keep them with larger or more aggressive fish, especially if you don’t want your beautiful new darter to end up as someone else’s lunch. These bright little fish are very shy when first introduced to their new home, so it is best to add them last and then watch to see how they interact with others.

Rainbow darter care

rainbow darters

The rainbow darter is a very unique fish to keep in an aquarium. Unlike most darters that spend much of their time burrowed in sand or other substrates, E. caeruleum will actually spend much of its time swimming on top of the substrate and looking for food.

They are very active swimmers and will do well in tanks with lots of water flow as well as open swimming areas. They can be kept with other darters but they tend to nip fins if they’re not added at about the same time. As far as tank mates go, these fish have been kept successfully with many different species of small tetras, rasboras, livebearers, and killifish.

They also do well when kept alone, as long as there is enough space for them to swim around freely without feeling crowded by others.

What do darter fish eat?

Etheostoma caeruleum are omnivores; their diet mainly consists of filamentous algae, small crustaceans, and insect larvae. They also consume detritus, a general term for dead organic matter. Because they spend most of their time in flowing water, they’re easily identified by their upturned mouth and chin. This helps them collect food while swimming upstream in swift currents.

Lifespan

rainbow darters

Rainbow darters can live for around 4 years in captivity with good care.

Parasites and diseases

Because rainbow darters are so small, they have fewer natural predators than their larger cousins. However, these fish do face a number of threats from parasites and diseases. One common parasite is a type of flatworm known as an anchor worm. These parasites latch onto rainbow darter fins, which can interfere with swimming and cause injury or infection. Additional symptoms associated with anchor worms include tissue loss and blood-stained scales.

In addition to anchor worms, rainbow darters may also contract bacterial infections such as fin rot and fungus infections like ich. Ich causes lesions on affected areas of skin that often appear white in color. If you notice any of these symptoms in your fish, be sure to treat them immediately to prevent further damage.

Predators

The rainbow darters can live up to 10 years if properly cared for but in nature, it rarely lives longer than 2 years due to predators, disease, and human interference. These fish are preyed upon by larger fish like bass, pike, catfish, sunfish, and walleye.

Do rainbow darters make good pets?

Rainbow darters make for great starter fish. Their small size and peaceful nature make them ideal for tanks with a capacity of 10 gallons or less. And if you’re looking to add some color to your tank, Etheostoma caeruleum is one of those fish that can do it all. They’ll school together, and they are perfect for anglers wanting some action in their tank.