Caring for Rainbowfish: Diet, Breeding, Tank Setup, and Ideal Tankmates

Introduction to Rainbowfish

Rainbowfish are popular in home aquariums due to their brilliant, shifting colors that seem to change as they swim. They are native to Australia, New Guinea, and surrounding islands, where they inhabit rivers, streams, and lakes. These regions offer a variety of water conditions, and Rainbowfish are known to adapt to seasonal changes in water levels and temperature. Known for their peaceful nature, they make ideal additions to community tanks, especially when kept in groups of at least six, as they are schooling fish.

There are many, many varieties of this fish, but the families that they are classed as belonging to are Atherinidae, Telmatheriidae, Melanotaeniidae, and Pseudomugilidae. Rainbowfish have been kept by aquarists since the early 20^th century, remaining a favorite due to their vibrant colors, hardiness, and lively swimming patterns. While their colors may appear dull in pet stores, they truly flourish once settled into a well-maintained home aquarium.

Tank Setup, Water Conditions, and Filtration

Rainbowfish are easy to care for and do well in planted tanks, where they will not disturb the plants. It is essential to provide ample open swimming spaces, as they prefer to swim in the top and middle layers of the tank. Tanks should focus on a larger surface area rather than depth, as Rainbowfish are surface feeders.

Rainbowfish thrive in slightly softer water, with ideal temperature ranges from 20–24°C (68–75°F) and pH levels between 6.0 and 7.0. Although they can adapt to harder water, it is not optimal for their long-term health.

Smaller species of Rainbowfish can be kept in tanks as small as 40 liters (10 gallons), but larger species require more space. For example, 80-liter (20-gallon) tanks can comfortably house up to 15 small Rainbowfish, while the largest species need 180-liter (40-gallon) tanks for the same number.

Ideal Filtration

Effective filtration is crucial for maintaining water quality in a Rainbowfish tank. There are several filtration options to consider:

• External filters (canister filters): Ideal for larger tanks, these provide strong mechanical, chemical, and biological filtration, essential for heavily stocked aquariums.
• Sponge filters: Great for breeding or fry tanks, as they offer gentle filtration without creating strong currents.
• Internal power filters: Suitable for smaller tanks, these provide good water movement and filtration for smaller Rainbowfish species.
• Undergravel filters: While less common, these can be used in lightly stocked tanks. However, regular maintenance is required to prevent waste buildup.

Suggested Tankmates for Rainbowfish

Rainbowfish are peaceful and social, making them great additions to community tanks. Here are some ideal tankmates that share similar water requirements:

• Tetras: Neon Tetras, Cardinal Tetras, and other small tetras are good companions.
• Corydoras: These peaceful bottom-dwellers are great tankmates as they inhabit different levels of the tank.
• Gouramis: Peaceful surface-dwelling species like Dwarf Gouramis are compatible with Rainbowfish.
• Rasboras: Harlequin Rasboras and other small rasbora species make good companions.

Avoid overly aggressive species or large fish that may stress or harass Rainbowfish. Cichlids and aggressive fin-nippers should not be housed with Rainbowfish.

Suitable Plants for Rainbowfish Tanks

Rainbowfish thrive in tanks with live plants, which improve water quality and provide cover. Some ideal plant choices for their tanks include:

• Anubias: Hardy and slow-growing, Anubias plants are perfect for a low-maintenance setup.
• Java Fern: Tolerant of a wide range of water conditions, Java Fern is a robust plant for Rainbowfish tanks.
• Vallisneria: Offering tall, flowing leaves, Vallisneria provides both shelter and open areas for swimming.
• Cryptocoryne: These plants offer excellent cover without overcrowding the tank.

These plants will create a natural environment for Rainbowfish, allowing them to feel more secure and display their best colors.

Rainbowfish Diet and Feeding

To keep Rainbowfish healthy and vibrant, provide a varied, well-balanced diet. They are omnivores, consuming both animal and plant matter. Their natural diet includes insects, insect larvae, small crustaceans, and even detritus. In aquariums, this can be replicated with high-quality flakes, granules, and live or frozen foods.

Feed them small, frequent meals rather than a single large meal, and avoid overfeeding, as they are greedy eaters. Because they are surface feeders, choose food that floats or lingers near the top of the water column. Live or frozen foods such as mosquito larvae, bloodworms, and brine shrimp are excellent choices. Freeze-dried foods, once rehydrated, can also provide necessary nutrients.

For variety, you can create homemade food mixes bound with gelatin and freeze them for later use. Regular feeding of live food mimics their natural foraging behavior and keeps them engaged and healthy.

How to Successfully Breed Rainbowfish

Sexing Rainbowfish is relatively easy, with males generally being more colorful and having longer dorsal and anal fins. To breed them, provide a breeding tank of 40–50 liters (10–15 gallons) with a thin gravel substrate and spawning mops or moss where eggs can be deposited. Males will display their vibrant colors and extended fins to court the females, and spawning typically occurs in the morning.

To trigger breeding, raise the tank temperature by 2–3 degrees. Feed the breeding pair a diet rich in protein for two weeks prior to breeding to increase the number of eggs. The eggs will attach to the spawning mops, and it’s best to move the mops to a separate container with an air stone to ensure water flow and prevent the parents from eating the eggs.

After hatching, all that should be placed in the rearing tank is a sponge filter to keep the water clean without creating excessive water flow. Any substrate or décor will only increase the risk of contamination. The sponge filter should be rinsed regularly, and the temperature should be set between 24–28°C (75–82°F). Perform small water changes every couple of days, being careful not to siphon out fry, and keep the tank clean by removing uneaten food and waste to reduce the chance of contamination.

Fry should be fed several times a day with a varied diet. Initially, they can survive on their yolk sacs for the first 2 days, but then should be fed infusoria or newly hatched brine shrimp. Infusoria can be easily prepared by adding a potato peeling to clean water and leaving it for a few days until the water becomes cloudy from infusoria growth. After a week or two, fry can start eating larger foods such as micro worms or vinegar worms.

As with all fry, mortality rates can be high, but this can be reduced with regular tank cleaning and feeding small, frequent meals. Fry that do not show signs of healthy growth (e.g., their stomachs do not swell after eating) should be monitored, and alternative smaller foods should be tried. Separate fry by size to prevent competition for food, allowing smaller fry to catch up. After 10–12 weeks, fry are large enough to be moved into a community tank, though they should be gradually weaned onto flake foods first.

Popular Rainbowfish Species

• Bedotia geayi (Madagascar rainbowfish)
• Bedotia madagascariensis (Rainbowfish)
• Chilatherina bleheri (Bleher’s rainbowfish)
• Glossolepis dorityi (Dority’s rainbowfish)
• Glossolepis incisus (Red rainbowfish)
• Glossolepis wanamensis (Wanam rainbowfish)
• Iriatherina werneri (Threadfin rainbowfish)
• Marosatherina ladigesi (Celebes rainbowfish)
• Melanotaenia affinis (New Guinea rainbowfish)
• and more here