--- type: species title: "GloFish Tetra Care Guide: Tank Setup, Diet, and Compatible Tank Mates" slug: "glofish-tetra" category: "freshwater" scientificName: "Gymnocorymbus ternetzi" subcategory: "Tetra" lastUpdated: "2026-04-24" readingTime: 9 url: https://www.fishstores.org/species/glofish-tetra --- # GloFish Tetra Care Guide: Tank Setup, Diet, and Compatible Tank Mates *Gymnocorymbus ternetzi* Beginner guide to GloFish Tetras — tank size, water parameters, feeding, tank mates, and where to find healthy fish. ## Species Overview The GloFish Tetra is a fluorescent variant of the Black Skirt Tetra (*Gymnocorymbus ternetzi*), a peaceful schooling fish native to the Paraguay and Guapore river basins of South America. The base species has been a community-tank staple since the 1930s, prized for its tall, diamond-shaped body and easy-going nature. The GloFish line takes that same workhorse fish and adds a stable, inheritable fluorescent color produced by a jellyfish or sea-anemone protein gene inserted at the embryo stage. That genetic origin is the key thing to understand before you buy. A GloFish Tetra is not painted, dyed, or injected. It is a transgenic Black Skirt Tetra, and outside of the color, every aspect of its care — tank size, diet, water chemistry, temperament — is identical to the parent species. If you can keep a Black Skirt Tetra alive, you can keep a GloFish Tetra alive. | Field | Value | | ----------- | ---------------------------- | | Adult size | 1.5–2 in (4–5 cm) | | Lifespan | 3–5 years | | Min tank | 20 gallons | | Temperament | Semi-aggressive (fin nipper) | | Difficulty | Beginner | | Diet | Omnivore | ### What Is a GloFish Tetra? GloFish Tetras are *Gymnocorymbus ternetzi* — the standard Black Skirt Tetra — modified to express fluorescent proteins in their muscle tissue. The original GFP (green fluorescent protein) gene was isolated from the jellyfish *Aequorea victoria* and adapted for use in zebrafish; later RFP (red fluorescent protein) variants came from corals and sea anemones. Yorktown Technologies (now GloFish LLC, owned by Spectrum Brands) brought the line to U.S. retail in 2003. The fluorescence is genetic, not topical. The fish glow most visibly under blue or actinic LED lighting, but the color is present 24/7 — even under regular daylight. Offspring inherit the trait through normal Mendelian inheritance, which is exactly why GloFish LLC restricts breeding for resale. For the unmodified base species, see our [Black Skirt Tetra page](/species/black-skirt-tetra). > **GMO origin in plain language** > > GloFish Tetras carry a fluorescent protein gene (GFP from jellyfish or RFP from coral/anemone) inserted into their DNA at the embryo stage. Care is identical to the standard Black Skirt Tetra. They are not painted, dyed, or injected. The fish are banned from sale in California and across the European Union, so check local regulations before purchasing. ### Color Variants Available GloFish Tetras are sold under six trademarked color names: Starfire Red, Electric Green, Sunburst Orange, Cosmic Blue, Galactic Purple, and Moonrise Pink. Each color corresponds to a different fluorescent protein, and within a single color line, individual fish are essentially identical genetically. A "Cosmic Blue" tetra will not turn purple over time, and a stressed Sunburst Orange will not lose its color permanently. Color does dim noticeably when a fish is stressed, sick, or kept in poor water — that visible fade is one of the more useful diagnostic tools you get with a GloFish, since the same dimming on a regular Black Skirt would be much harder to spot. > **Color is permanent — fading means stress** > > Unlike dyed fish, a GloFish's fluorescence never wears off. If your GloFish Tetra looks dull or muted, treat it as a health signal. Test water parameters first, check for aggression from tank mates, and look for clamped fins or rapid gill movement. ### Size & Lifespan Adult GloFish Tetras top out around 1.5 to 2 inches in body length, the same as wild-type Black Skirts. Females are slightly larger and rounder; males are smaller with a thinner, more pointed dorsal fin. With clean water, a varied diet, and stable temperatures, a healthy individual lives 3 to 5 years in the home aquarium. The fish reaches near-adult size in 6 to 8 months and is sexually mature around 9 to 12 months. Color intensity tends to peak after the first year, when muscle mass fills out enough to carry the fluorescent expression at full saturation. ## Water Parameters & Tank Requirements GloFish Tetras are forgiving on parameters but unforgiving on instability. The genetic modification does not change their water needs — these are still tropical South American tetras, and they want warm, slightly soft, neutral-to-mildly-acidic water that doesn't swing day to day. ### Ideal Water Conditions Target a steady 75 to 78°F with a quality heater. The fish tolerate a wider 72 to 82°F range, but rapid swings of more than 4°F in 24 hours are the most common trigger for ich outbreaks in tetra tanks. pH should sit between 6.0 and 7.5, with general hardness between 5 and 20 dGH. Most tap water in the U.S. lands inside this range with no adjustment needed. Ammonia and nitrite must read zero before you introduce any fish. Nitrate should stay under 30 ppm with weekly 25 percent water changes. Cycle the tank fully — measurable nitrate, zero ammonia, zero nitrite, sustained for at least a week — before adding your first GloFish. See our [freshwater fish guide](/guides/freshwater-fish) for the full cycling sequence. ### Minimum Tank Size & Schooling Space A 10-gallon tank is the absolute minimum for a small group, but it cramps adult fish and amplifies the fin-nipping that already comes with the species. The realistic minimum is a [20-gallon long](/guides/20-gallon-fish-tank), which gives you the horizontal swimming distance a school of 6+ tetras actually uses. The longer footprint matters more than the height. GloFish Tetras swim laterally in the middle and upper third of the tank — depth doesn't help them, length does. A 20-long (30 in × 12 in × 12 in) is dramatically better for an active school than a 20-tall, even though both hold the same volume of water. ### Filtration, Flow & Lighting A hang-on-back filter rated for 30 gallons or a sponge filter plus a small powerhead handles a school of 6 to 10 tetras in a 20-gallon. Aim for low-to-moderate flow — these are not strong swimmers, and a high-current tank stresses them and damages fins over time. Baffle the filter outflow if you see fish hugging the corners. Lighting is where you make the fluorescence pop. Under standard white LED light, GloFish Tetras look colorful but not dramatic. Switch to a blue actinic or dedicated GloFish LED fixture (peak emission around 395 to 470 nm) and the fluorescent proteins light up under the UV-end stimulation. A black-light effect against a black or very dark substrate produces the postcard look. ### Substrate & Décor Dark substrate amplifies the glow. Black sand, dark gravel, or seeded blackwater substrate all work — light or white substrate washes the fluorescence out and reflects the actinic lighting in a way that flattens the color. Stick to smooth-edged hardscape; tetras can shred their tall dorsal fins on sharp slate or jagged rock. Live or silk plants are both fine. Live options like Java fern, Anubias, and Vallisneria provide cover without competing with the lighting setup. Avoid plastic plants with hard, sharp leaf edges. A few floating plants help diffuse the lights and give the school a sense of overhead cover, which reduces stress and visible fin-nipping. ## Diet & Feeding GloFish Tetras are omnivores in the loosest sense — they will eat almost any small, sinking or floating food you put in the tank. Variety matters more than brand. ### What GloFish Tetras Eat A high-quality tropical flake or micro-pellet works as the daily staple. Look for a protein content of 35 to 45 percent and avoid bargain-brand flakes that list filler grains as the first ingredient. Supplement two or three times a week with frozen brine shrimp, daphnia, bloodworms, or live equivalents — these protein-rich treats keep colors saturated and trigger natural foraging behavior. In the wild, the parent species eats small crustaceans, insect larvae, and plant matter from slow-moving Brazilian river basins. A purely flake-based diet works but produces duller fish over time. Rotating in frozen foods is the simplest single change you can make to improve color and condition. ### Feeding Schedule & Portion Size Feed twice daily, morning and evening, in portions the school finishes within two minutes. Uneaten food sinks, decays, and spikes ammonia in a 20-gallon tank faster than most beginners expect. A pinch of flake the size of the fish's eye, scaled to your school size, is the right starting amount. Skip one feeding per week to let the fish clear their digestive system and reduce the bioload. GloFish Tetras handle a fast day without complaint, and the practice keeps adults from becoming bloated or constipated as they age. ## Tank Mates & Compatibility The semi-aggressive label on GloFish Tetras is real, and it traces back to the same fin-nipping streak the standard Black Skirt has. Schooling correctly is the single biggest factor in keeping that behavior contained. > **Avoid long-finned tank mates** > > GloFish Tetras are well-documented fin nippers. Do not house them with bettas, fancy guppies, angelfish, long-finned goldfish, or any other species with trailing fins. The tetras will pick at the trailing tissue until it is shredded, and the slow-moving target fish has no defense. ### Best Community Tank Mates Other GloFish varieties — including [GloFish Danios](/species/glofish-danio) — pair naturally and share the same lighting and care requirements. Standard tetras like neons, ember tetras, and rummynose tetras work well in larger schools. Bottom dwellers including Corydoras catfish, Otocinclus, and Kuhli loaches occupy a different layer of the tank and avoid most conflict. Small rasboras (harlequin, chili, lambchop) and peaceful livebearers like platies and mollies — provided the livebearers don't have long, flowing tails — also fit a community setup. The unifying trait is short fins, similar size, and a non-confrontational temperament. ### Fish to Avoid Skip fin-nippers like tiger barbs and serpae tetras — combining two nippy species in one tank multiplies the chaos rather than canceling it out. Avoid large or aggressive cichlids, which view 2-inch tetras as snacks. Bettas are a coin flip, and the long-finned varieties (halfmoon, crowntail) are nearly always a bad outcome regardless of betta personality. Goldfish belong to a completely different temperature range and bioload tier — don't mix. Large gouramis and oscars will outcompete or eat tetras outright. ### Keeping a Proper School The minimum group is six fish, and eight to ten is meaningfully better. In a school of three or four, the dominant individual fixates on tank mates and the fin-nipping concentrates on whatever weaker fish is nearby. In a school of eight, the aggression disperses across the group and individual fish get harassed less often. > **Schooling 6+ disperses aggression** > > Buying "just two or three" GloFish Tetras to start is the most common beginner mistake with this species. The smaller the group, the more concentrated the bullying becomes. Plan for a minimum of 6 from day one — the price difference is minor, and the behavioral difference is dramatic. ## Common Health Issues GloFish Tetras share the disease profile of standard Black Skirts. Stress and water quality are the upstream cause of nearly everything you'll see. ### Ich & Fin Rot Ich (*Ichthyophthirius multifiliis*) presents as small white grains of salt across the body and fins. Treatment is straightforward — raise the tank temperature gradually to 82°F over 24 hours and dose an aquarium-safe ich medication for the full label cycle (typically 7 to 10 days). Increased temperature accelerates the parasite's life cycle and shortens the treatment window. Fin rot shows up as ragged, white-edged fins that progressively erode toward the body. The cause is almost always poor water quality combined with bacterial infection in the damaged tissue. Fix water first — large water change, filter clean, parameter check — then dose with a broad-spectrum antibacterial if the rot doesn't reverse within a few days. ### Signs of Stress in GloFish Tetras The fluorescent color fades visibly under stress, which is one of the genuine practical advantages of keeping the modified line. A dimmed or muted GloFish is broadcasting a problem before you'd notice anything wrong with a non-fluorescent fish. Look also for clamped fins (held tight to the body instead of flared), rapid gill movement above 90 beats per minute, hiding behavior from a normally bold school, and loss of appetite. Two or more of these signs together justify an immediate water test and a 25 percent water change. ### Copper Sensitivity Note Tetras as a family are mildly sensitive to copper-based medications. Most ich and parasite treatments contain copper at therapeutic doses, and tetras tolerate them at standard levels — but always dose carefully, never overshoot the manufacturer's instructions, and never combine medications. If you keep shrimp or snails in the same tank, copper treatments will kill them outright; remove invertebrates to a quarantine tank before dosing. ## Breeding GloFish Tetras Breeding the species is biologically simple but legally restricted, which is the unusual angle of this fish. ### Legal Restrictions on Breeding GloFish Tetras are sold under a GloFish LLC licensing agreement that prohibits intentional breeding for resale or distribution. The fluorescent protein traits are patented intellectual property, and reselling fry — even to friends or local aquarium clubs — is not permitted under the terms. Accidental home spawning is not prosecuted, and you do not need to dispose of fry that hatch in your tank. But if your goal is to set up a breeding program, the GloFish line is the wrong starting point. A standard Black Skirt Tetra colony is unrestricted and breeds the same way. ### Accidental Spawning The fish are egg-scatterers. A pair conditioned with frozen foods and triggered by a small water change with cooler, softer water will scatter sticky eggs across plants and substrate. Adults eat their own eggs and fry without hesitation, so accidental spawning rarely produces visible fry in a community tank — the eggs are gone within hours. If you spot eggs and want to save fry, transfer the eggs to a separate 5-gallon tank with a sponge filter and gentle aeration. Fry hatch in 24 to 36 hours and need infusoria or commercial liquid fry food for the first two weeks before they can take baby brine shrimp. ## Where to Buy & What to Look For GloFish Tetras are widely stocked at chain pet stores and most local fish stores in states where they are legal. California and the entire European Union prohibit sale, and a few municipalities have additional restrictions — check local rules before driving anywhere. ### Finding Healthy GloFish Tetras at Your Local Fish Store Walk the aisle slowly. A healthy school is mid-water, actively swimming, and visibly schooling rather than scattered across the tank. Color should be saturated and bright under the store's lighting — even non-actinic lighting should produce a visible glow. Fish that look dim or pale are stressed, sick, or both. > **What to inspect before you buy** > > Look for active schooling behavior in the middle of the tank, bright fluorescence under store lighting (not dim or muted), intact dorsal and tail fins with no nipping damage, no white spots or fuzzy patches, and no dead fish in the same display tank. Ask the store to feed the fish so you can confirm they are eating before you commit. Avoid any tank with visibly dead fish floating or sunken in corners, fish hanging at the surface gulping air, or obvious ich on any tank inhabitant — disease in the system tank means disease in the fish you're about to buy. ### Price Range & What's Included Expect to pay $5 to $8 per fish at retail, with chain stores often pricing closer to $7 across all six color variants. Discounts on bulk purchases (6-packs or 10-packs) sometimes appear, particularly during back-to-school promotions when GloFish-branded starter kits are heavily marketed. GloFish-branded tank kits bundle a small aquarium (typically 3, 5, or 10 gallons), a fluorescent LED hood, filter, and starter accessories. The 3- and 5-gallon kits are too small for tetras as adults — they work for short-term display but you will outgrow them quickly. If you're starting from scratch, buy a 20-gallon long separately and add the GloFish blue LED bar as an upgrade. The math works out better and the fish are happier long-term. ## Quick Reference - **Tank size:** 20 gallons minimum (10-gallon absolute floor for short-term) - **Temperature:** 72–82°F (target 75–78°F) - **pH:** 6.0–7.5 - **Hardness:** 5–20 dGH - **Filtration:** HOB rated for 30 gal or sponge + low flow - **Lighting:** Blue actinic or GloFish LED for full fluorescence - **Substrate:** Dark — black sand or gravel amplifies color - **Diet:** Tropical flake or micro-pellet daily; frozen brine/daphnia 2–3x weekly - **Feeding frequency:** 2x daily, finish in 2 minutes; fast 1 day/week - **School size:** Minimum 6, ideally 8–10 - **Tank mates:** Other GloFish, neon and ember tetras, Corydoras, Otocinclus, harlequin rasboras, short-finned livebearers - **Avoid:** Bettas, fancy guppies, angelfish, tiger barbs, serpae tetras, large cichlids, goldfish - **Lifespan:** 3–5 years - **Adult size:** 1.5–2 in - **Difficulty:** Beginner — but plan for fin-nipping and school properly - **Legal note:** Banned in California and the EU; breeding for resale prohibited ## Frequently Asked Questions ### How many GloFish Tetras should be kept together? Keep a minimum school of 6. GloFish Tetras are social fish that become stressed and prone to fin-nipping when kept in smaller groups. A 20-gallon tank comfortably houses a school of 6-8 alongside peaceful community tank mates. ### Are GloFish Tetras dyed or genetically modified? GloFish Tetras are genuinely transgenic fish — they carry a fluorescent protein gene introduced at the embryo stage. They are not injected or dyed, and they pass the trait to offspring naturally. ### What do GloFish Tetras eat? GloFish Tetras are omnivores that readily accept high-quality flake food, micro-pellets, and frozen or live foods like brine shrimp and daphnia. Feed small amounts twice daily to maintain water quality. ### Can GloFish Tetras live with bettas? It depends on the individual betta. GloFish Tetras' bright colors and active movement can trigger aggression in some bettas. A 20-gallon+ tank with dense planting and a docile betta improves compatibility odds — monitor closely. ### Is it legal to breed GloFish Tetras? GloFish are sold under a licensing agreement that prohibits intentional breeding for resale. Accidental home spawning is not prosecuted, but selling or distributing the fry is not permitted under GloFish LLC's terms. --- *Source: [FishStores.org](https://www.fishstores.org/species/glofish-tetra)* *Last updated: April 24, 2026*