GloFish® Cosmic Blue® Danio

The GloFish® Cosmic Blue® Danio is a lively freshwater schooling fish with vivid fluorescent blue coloration. Based on the zebra danio, this active species is known for fast swimming, energetic group behavior, and frequent activity near the upper and middle areas of the aquarium.

Cosmic Blue® Danios are colorful under standard white aquarium lights and appear especially vivid under blue LED lighting. GloFish® fluorescent fish are not painted, injected, or artificially dyed. Their fluorescent coloration is inherited from their parents.

Key Features

• Bright Cosmic Blue® fluorescent coloration
• Active freshwater schooling fish
• Based on the hardy zebra danio
• Fast-moving upper- and midwater swimmer
• Best maintained in a group
• Suitable for established freshwater community aquariums
• Color is visible under white lighting and especially vivid under blue LEDs
• Not painted, injected, or artificially dyed
• Can school with other compatible GloFish® danio colors

Fish Information

• Common Name: GloFish® Cosmic Blue® Danio
• Fish Type: Fluorescent zebra danio
• Water Type: Freshwater
• Temperament: Generally peaceful, active, and energetic
• Adult Size: Approximately 2–2.5 inches
• Recommended Group Size: At least 6 danios
• Recommended Minimum Tank Size: 20 gallons, preferably a longer aquarium
• Swimming Level: Upper and middle levels
• Diet: Omnivore

Recommended Water Parameters

• Temperature: Approximately 72–80°F
• pH: Approximately 6.5–7.5
• Water Hardness: Soft to moderately hard
• Ammonia: 0 ppm
• Nitrite: 0 ppm
• Nitrate: Kept as low as practical through routine maintenance

Stable water quality is more important than reaching one exact pH or hardness value. Avoid sudden changes in temperature or water chemistry.

Schooling and Behavior

Cosmic Blue® Danios are highly social fish and should be kept in a group rather than alone. A school of at least six is recommended, although a larger group may display more natural behavior when aquarium space allows.

Different GloFish® danio colors can generally be combined in the same school. Compatible standard zebra danios may also be kept with them because they share similar behavior and care requirements.

Danios are fast and constantly active. Their energetic movement can overwhelm very slow, timid, or long-finned fish, so tankmates should be selected carefully.

Aquarium Setup

Provide a fully cycled, filtered aquarium with plenty of open horizontal swimming space. A longer aquarium is generally preferable to a tall, narrow tank because danios spend much of their time swimming back and forth.

• Use a properly cycled freshwater aquarium
• Provide reliable filtration and good oxygenation
• Leave ample open swimming room
• Add live or artificial plants around the sides and back
• Use a secure lid because danios may jump
• Provide moderate water movement
• Perform regular partial water changes
• Maintain a normal day-and-night lighting schedule

Lighting

Cosmic Blue® Danios remain colorful under ordinary white aquarium lighting. Blue LED lighting makes their fluorescent coloration appear especially vivid.

Lighting should not be left on continuously. GloFish recommends limiting aquarium lighting to no more than approximately 12 hours per day so the fish receive a regular period of darkness.

Compatible Tankmates

Choose peaceful, active community fish that can comfortably live with the danio’s fast swimming and energetic behavior.

• Other GloFish® danios
• Standard zebra danios
• Active tetras
• Peaceful barbs
• Rasboras
• Corydoras catfish
• Peaceful livebearers
• Small rainbowfish
• Other similarly sized, non-aggressive community fish

Avoid highly aggressive fish, species large enough to eat them, and very slow or delicate long-finned tankmates that may be stressed or chased.

Feeding

GloFish® Cosmic Blue® Danios are omnivores and should receive a varied diet of appropriately sized foods.

• Quality tropical flakes
• Micro pellets or small slow-sinking pellets
• Frozen brine shrimp
• Frozen daphnia
• Frozen or freeze-dried bloodworms as an occasional food

Feed small amounts once or twice daily, offering only what the fish can consume within a few minutes. GloFish also recommends its flake or MicroCrisp foods for danios, tetras, and barbs.

Acclimation

1. Turn off the aquarium lights before introducing the fish.
2. Float the unopened transport bag for approximately 15 minutes to equalize temperature.
3. Open the bag and gradually add small amounts of aquarium water.
4. Wait several minutes between additions.
5. Carefully net the fish into the aquarium.
6. Avoid adding transport water to the display aquarium when practical.
7. Leave the aquarium lights off for several hours while the fish settle.

Quarantine new fish before adding them to an established aquarium whenever a suitable quarantine system is available.

Important Care Notes

• Keep in a group rather than as a single fish.
• Provide ample horizontal swimming room.
• Use a secure aquarium lid.
• Do not add to an uncycled aquarium.
• Maintain stable temperature and water quality.
• Avoid overcrowding and incompatible tankmates.
• Provide a regular light-and-dark cycle.
• Never release aquarium fish into local waterways.
• Commercial reproduction of GloFish® fluorescent fish is restricted by the manufacturer’s licensing terms.

Frequently Asked Questions

Are Cosmic Blue® Danios dyed?
No. GloFish® fluorescent fish are not painted, injected, or dyed. Their bright fluorescent coloration is inherited.

Do they require special food or water?
No. Their general care is the same as standard zebra danios. Provide stable freshwater conditions and a varied, high-quality diet.

Do they glow in complete darkness?
No. Their fluorescence becomes visible when illuminated and appears especially vivid under blue LED aquarium lighting.

Can different GloFish® danio colors live together?
Yes. Different color varieties of GloFish® danios can generally be maintained together and count toward the same school.

Can I keep only one?
No. Danios are social schooling fish and should be maintained in a group of at least six.

Are they suitable for a five-gallon aquarium?
No. They are fast, active schooling fish that require substantially more swimming room. A 20-gallon-long-style aquarium is a more appropriate starting point for a group.

Can they live with GloFish® tetras?
They may be housed with compatible GloFish® tetras in an appropriately sized community aquarium, but danios and tetras should each have enough members of their own species group.

Will the blue color fade?
The inherited color remains with the fish, although its appearance may vary with lighting, health, stress, diet, and water quality.

Available at Tropical Treasures Wyo

GloFish® Cosmic Blue® Danios are available at Tropical Treasures Wyo in Cheyenne, Wyoming, when in stock. Live fish are available for in-store purchase or local pickup only and are not available for shipping.

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