Green Neon Tetra (Paracheirodon simulans)

Green Neon Tetra (Paracheirodon simulans) is a very small South American shoaling fish with a bright blue-green lateral stripe and a more restrained red area than the familiar Neon or Cardinal Tetra. Its compact size makes it attractive for carefully planned planted and blackwater-style aquariums, but small does not mean undemanding. The species is best suited to a mature, stable aquarium with warm, very soft, mildly acidic water and a properly sized group.

This listing is for one unsexed fish per selected quantity. Choose the required size option in the selector. A quantity of ten means ten individual fish; it does not guarantee a particular sex ratio, breeding group, matching colour, or fish identical to those illustrated. Green Neon Tetras are social, so plan the complete group and aquarium before ordering rather than buying one fish to keep alone.

The available size bands are 0,5-1 cm, 1,5-2 cm, 1-2 cm and 2-2.5 cm. These are approximate dispatch bands, not exact measurements or separate colour forms. The commas in two selector labels are decimal separators. Natural variation is expected, and a fish may be near either end of the selected band.

The accepted scientific name is Paracheirodon simulans. Green Neon Tetra and Green Neon are the clearest English trade names; False Neon Tetra and Green Cardinal also occur in references. This is a distinct species, not a dyed fish, a fluorescent engineered form, or a colour stage of Paracheirodon innesi. Correct identification separates its care from superficially similar fish.

Green Neon Tetra care at a glance

Accepted scientific name	Paracheirodon simulans (Géry, 1963)
Common names	Green Neon Tetra; Green Neon; False Neon Tetra; Green Cardinal
Order	Characiformes
Genus	Paracheirodon
Published size record	2.0 cm standard length; plan for roughly 2.5-3 cm total length in aquarium care
Care level	Moderate / intermediate, mainly because stable soft water and a mature aquarium matter
Temperament	Peaceful and social; keep as a shoal
Group planning	At least 10, with a larger group preferable when aquarium space allows
Aquarium planning guide	About 60 litres and 60 cm long as a conservative starting point for 10 fish
Temperature	23-27 C in a stable managed aquarium
pH	About 5.5-6.5
Hardness	Very soft water, approximately 1-5 dGH
Diet	Very small prepared foods plus suitably sized live or frozen invertebrate foods
Aquarium region	Mostly middle levels
Sale unit	One unsexed fish in the selected approximate size band

The aquarium and group figures above are conservative planning guidance rather than universal scientific thresholds. They combine the fish's social behaviour, need for horizontal swimming room, small mouth, sensitivity to unstable water and the practical value of extra water volume. A larger shoal, mixed community or complex aquascape needs more room. Use the tank-volume calculator to estimate the working volume after substrate, wood and other displacement.

Identity, size and natural range

Paracheirodon simulans is a valid species in the neon-tetra group. Eschmeyer's Catalog of Fishes records the accepted combination, while GBIF also lists the historical combinations Cheirodon simulans and Hyphessobrycon simulans. Family placement differs among current taxonomic backbones, so the species name is a more stable identifier than assigning one family without qualification.

FishBase records a maximum of 2.0 cm standard length. Standard length excludes the tail fin, so an aquarium planning figure of roughly 2.5-3 cm total length is reasonable while still recognising that individual fish vary. This distinction matters when comparing a dispatch band with adult size: a 0.5-1 cm fish is a very small juvenile, not a permanently miniature version of the species.

The published distribution covers the upper Negro and Orinoco river basins in South America. Field research has also sampled the species in interfluvial palm-swamp habitat in the middle Rio Negro region. These habitats can be shallow, vegetated, seasonally flooded and chemically very soft. They are more complex than the simple phrase "blackwater stream", so an aquarium does not need to copy one photograph to meet the fish's needs. The useful principles are stable soft water, shade, cover, gentle movement and clean conditions.

A modern phylogenetic study of neon tetras includes P. simulans sampled from palm-swamp habitat. That work supports treating Green Neon Tetra as its own biological entity rather than assuming that every Neon or Cardinal Tetra recommendation applies unchanged. Similar-looking species can share broad needs, but adult size, markings, distribution and suitable companions should still be checked for the exact fish being purchased.

Choosing a size option and quantity

Selector label	What one selected quantity means	Planning note
0,5 - 1 cm	One unsexed fish in the approximate 0.5-1 cm band	Exceptionally small fish need suitably fine food and gentle tank mates
1,5 - 2 cm	One unsexed fish in the approximate 1.5-2 cm band	Still below the practical adult total-length plan
1-2 cm	One unsexed fish in the approximate 1-2 cm band	Natural size variation within the band is expected
2-2.5 cm	One unsexed fish in the approximate 2-2.5 cm band	A larger listed grade, not a guaranteed adult or sexed fish

Choose quantity around welfare and available space. Ten is a sensible minimum planning group because this is a social shoaling species; a larger group often creates a more coherent display and spreads social attention more naturally. Do not use that recommendation to overstock a small tank. Filtration capacity, mature biological media, floor plan, plants, existing livestock and maintenance routine all limit the number the aquarium can support.

When combining different listed sizes, make sure every fish can reach food. Very small juveniles can be outcompeted by larger, faster fish even when no direct aggression occurs. A group of broadly similar size is easier to feed and observe. If an exact current measurement is essential, ask through the contact page before ordering rather than assuming the gallery provides reliable scale.

Aquarium size and group behaviour

For a first group of ten, plan around a mature aquarium of about 60 litres with a length close to 60 cm. This is not a claim that any container holding 60 litres is automatically suitable. A long, planted aquarium offers more useful swimming room and visual cover than a tall vessel with the same nominal volume. A group larger than ten, or a mixed community, is better in 75 litres or more with additional horizontal space.

Green Neon Tetras usually occupy the middle levels and move as a loose social group. The shoal may draw closer when startled, during a disturbance or in open water, then spread out again once secure. Constant tight formation is not the only sign of normal behaviour. The better welfare signals are that fish use the aquarium, feed without panic, maintain body condition and are not persistently isolated, chased or pinned in one area.

Keeping one or two fish does not reproduce the social setting for which the species is adapted. A token group of six may survive, but a group of ten or more gives more scope for natural interaction without placing all attention on a few individuals. The recommendation is about social planning, not a promise that every fish in a larger group will behave identically.

A specialist Green Neon Tetra care guide from Aquarium Co-Op also recommends increasing the group to at least ten and describes the species as a peaceful midwater fish. Its 10-US-gallon example is not treated as a universal minimum here. The more conservative 60-litre starting point provides extra water volume and swimming room for a ten-fish group, while the final choice still depends on the aquarium's usable footprint, filtration and other livestock.

Small aquariums change temperature and chemistry quickly. Extra water volume gives more buffering time when feeding, evaporation or maintenance changes conditions. It does not replace testing or water changes, but it reduces how abruptly a mistake affects the whole system. This is one reason the practical recommendation is more generous than a minimal nano-tank calculation based only on the fish's body length.

Temperature, pH and hardness

Maintain a stable 23-27 C. FishBase publishes this as the species' tropical range, and the middle of it is a sensible everyday target. A field study in middle Rio Negro palm swamps recorded much higher temporary habitat temperatures, including a maximum of 35.2 C at sampled P. simulans sites. That observation may indicate tolerance, but it is not a reason to keep aquarium fish near a stressful extreme.

Use a dependable heater and thermometer where the room cannot hold the chosen range. Avoid positioning a small aquarium beside a radiator, cold window or strong sunlight. A stable 25 C is more useful than repeatedly moving between the published limits. Any planned temperature change should be gradual and should also suit every other species in the aquarium.

The water should be very soft and mildly acidic. A practical managed target is around pH 5.5-6.5 and approximately 1-5 dGH. FishBase gives a narrower pH reference of 5.5-6.0 and hardness up to about 4 dH; the slightly wider planning range recognises normal aquarium measurement and acclimation limits without turning hard alkaline water into a recommendation.

Do not lower pH rapidly with an uncontrolled chemical dose. Low-mineral water has limited buffering, so pH can move unexpectedly if alkalinity is exhausted. Aquarists using reverse-osmosis water should remineralise and measure consistently rather than using pure water without a plan. Match source and aquarium conditions carefully, then make any adjustment over time. The water-parameter tool can help compare planned livestock requirements.

Planning and maintaining soft water safely

Start with measurements rather than a product chosen only because its label mentions pH. Test the aquarium and replacement water for temperature, pH and general hardness; carbonate hardness or conductivity can provide additional context when managing a very soft system. Liquid tests, meters and strips have different limits, so follow the manufacturer's method, keep equipment clean and look for repeatable trends instead of reacting to one surprising reading.

If the tap supply is substantially harder than the intended aquarium conditions, a measured blend of reverse-osmosis and tap water may be more controllable than adding acid to hard water. The chosen method must produce the same safe replacement water each time. Record the recipe, temperature and readings, and make a small test batch before using it in the aquarium. Never assume that all reverse-osmosis units, remineralising products or local tap supplies produce identical results.

Very soft water requires deliberate mineral management. Pure reverse-osmosis water is not automatically suitable for fish, plants or biological filtration, and a target pH by itself does not describe all of the dissolved chemistry. Use an appropriate remineralising approach when needed and avoid large unmeasured changes. If the current aquarium is hard and alkaline, it may be better to choose livestock suited to that water than to force a fragile low-mineral setup without the equipment or experience to maintain it.

Evaporation removes water but leaves most minerals behind. Top up evaporated water according to the system's established method; do not treat a top-up as a water change because it does not remove nitrate or other dissolved waste. During a real water change, replace water with a prepared mix that closely matches the aquarium. This reduces cumulative drift and is especially important in a small aquarium where a bucket can represent a large percentage of the total volume.

Botanicals, wood and leaf litter may release tannins and mildly influence chemistry, but they are not a precise substitute for testing or controlled source-water preparation. Their effect depends on quantity, age, water buffering and maintenance. Add them gradually, inspect for excessive decay and keep enough circulation that organic material does not create stagnant pockets. A tea-coloured aquarium can still have unsuitable hardness, ammonia or oxygen levels.

Filtration, oxygen and maintenance

Use mature biological filtration with a gentle to moderate current. A sponge filter, air-driven system or suitably adjusted internal or external filter can work. The intake must be safe for the smallest selected fish, and the outflow should not force the shoal to struggle continuously. Provide areas of calmer water as well as enough circulation to prevent waste collecting behind wood and plants.

Warm water holds less oxygen than cool water, so surface movement and sensible stocking remain important even for a species associated with quiet habitats. Gentle does not mean stagnant. Watch for rapid breathing, crowding near the surface or fish avoiding a poorly circulated zone. These signs have several possible causes and should prompt water testing and a complete husbandry check rather than an immediate assumption about one disease.

OATA's freshwater water-quality guidance explains the role of biological filtration and states that ammonia and nitrite should remain at zero in a mature aquarium. Nitrate should be controlled with stocking, feeding, plant growth and regular water changes appropriate to the setup. Change enough water to maintain stability without causing a sudden shift in temperature, pH or mineral content. Match new water before adding it, especially when the aquarium is maintained softer than the tap supply.

A newly filled aquarium is not mature simply because the water looks clear. The RSPCA aquarium guide recommends fishless cycling and adding fish only after ammonia and nitrite have risen and returned to zero; it also notes that there is no exact cycling duration. Green Neon Tetras are a poor choice for an uncycled system or a tank that still swings after every meal. Establish the filter, confirm stable test results and make sure fine food can be offered without fouling the substrate before ordering a group.

Plants, substrate, cover and lighting

A dark substrate, wood, leaf-litter tones and areas of dense planting help the iridescent stripe stand out and give the fish options between open and sheltered water. Java fern, Cryptocoryne, moss and other aquarium plants can provide useful structure when their own requirements suit the setup. The aquarium can be a strict regional display, a planted community or a modern aquascape; welfare does not depend on one decorative style. Keep enough open midwater for the group to move together.

Floating plants and taller background growth can break up overhead light. Subdued to moderate lighting is often more comfortable than a bright, exposed layout, but plants still need enough light to remain healthy. Use a timer and provide a predictable day-night cycle. The fish's colour may look less intense after darkness or during stress and become brighter once settled; colour alone is not a guaranteed measure of health.

Fine sand or smooth gravel both work when kept clean. Secure wood and stones so maintenance cannot trap fish, and avoid narrow gaps that a startled shoal could enter but not leave. Leaves and botanicals can add cover and tannins, but they also decompose. Add them deliberately, monitor water chemistry and remove material if it begins to foul the aquarium.

Every Green Neon Tetra aquarium should have a fitted cover. Tiny fish can pass through surprisingly small openings, particularly during transfer or sudden disturbance. Check around cables, pipes and filter returns. A cover also reduces evaporation, which is helpful when mineral concentration and water level need to remain stable.

Feeding Green Neon Tetras

The mouth is very small, so food size matters as much as food type. Use a quality micro-pellet, finely crushed flake or another complete prepared food that the fish can take easily. Supplement with suitably sized frozen or live foods such as Cyclops, small daphnia or baby brine shrimp. The goal is dietary variety and reliable intake, not dependence on one rich treat.

Offer small portions and observe the whole shoal. Food should remain available long enough for shy fish to feed but should not settle everywhere and decay. One or two modest feeds per day can work for established fish; very small juveniles may benefit from carefully divided fine feeds when filtration and maintenance can support them. Adjust to body condition, group competition and the nutritional density of the food rather than following a rigid clock.

Place food across more than one part of the surface or flow path if dominant or faster fish take everything first. Check that the smallest fish are swallowing food, not merely approaching it. Crush prepared food before it enters the aquarium when necessary. Thaw frozen food safely and avoid adding a large volume of packing water or uneaten fragments.

Green Neon Tetras are not algae-control fish. They may investigate tiny organisms or particles on surfaces, but they will not replace grazing livestock or correct an algae problem. They can also eat newly hatched shrimp if those prey fit in the mouth. Adult dwarf shrimp may coexist in a densely planted aquarium, but shrimp reproduction cannot be guaranteed in the presence of any small opportunistic fish.

Feeding different listed sizes

The smallest 0.5-1 cm grade needs particular attention because a food that looks fine to an adult fish may still be too large. Powdered or crushed complete food should remain nutritionally balanced rather than consisting only of dust from one ingredient. Offer a tiny amount where the fish are already holding in the water and watch for swallowing. If food repeatedly passes untouched, review particle size, flow, stress and water conditions before adding more.

Fish in the 1-2 cm and 1.5-2 cm bands can usually take a wider range of fine foods, but the group should still receive pieces small enough for every member. The 2-2.5 cm option is a larger grade, not permission to use large pellets intended for much bigger community fish. A food can fit into the mouth yet still be difficult to digest or nutritionally incomplete, so choose a product designed for small tropical fish and rotate suitable supplements.

Body shape is more useful than a fixed number of granules. View the group from the side and above when practical: fish should not become hollow through missed meals or remain visibly swollen after repeated heavy feeding. Growth rates vary with age, temperature, diet, competition and health, so this listing does not promise that a purchased size band will reach another band by a particular date. Consistent moderate feeding and clean water are safer than trying to accelerate growth.

When a community contains bottom-feeding fish, make sure food reaches them without overfeeding the tetras first. Conversely, sinking all food immediately can leave midwater fish underfed. Combining a suitable feeding pattern with observation is better than adding several foods at once. Remove obvious excess where possible and include uneaten food in the maintenance assessment if nitrate rises or the substrate begins to foul.

Temperament and compatible tank mates

This is a peaceful species, but compatibility depends on more than aggression. The most suitable companions are small, calm fish that share the same warm, soft, acidic water and do not outcompete a tiny tetra at feeding time. Similar body size does not automatically mean similar water requirements, and a fish described broadly as a community species may still be unsuitable.

Potential companion	Planning guidance
Small peaceful tetras or rasboras	Consider only species with overlapping temperature, pH, hardness and space needs
Small Corydoras	Possible when the exact species shares the warm soft-water range and has enough floor space
Adult dwarf shrimp	May coexist with cover, but shrimplets can be eaten
Guppies and hard-water livebearers	Usually a poor long-term water-chemistry match
Large, aggressive or fast predatory fish	Avoid because of stress, injury and predation risk

Use the tank-mate tool to build a shortlist, then verify each candidate independently. Introduce livestock only when the aquarium can support the combined adult size and waste load. Keep a plan for separation if a normally peaceful combination behaves differently in the actual tank.

Watch for persistent hiding, one fish separated from the group, torn fins, repeated chasing, loss of feeding access or a shoal compressed into one corner. Correct the cause rather than simply adding more livestock. Flow, light, lack of cover, water mismatch and an overbearing companion can all create behaviour that looks like a social problem.

Green Neon, Neon and Cardinal Tetra comparison

Feature	Green Neon Tetra	Neon Tetra	Cardinal Tetra
Scientific name	Paracheirodon simulans	Paracheirodon innesi	Paracheirodon axelrodi
Relative adult size	Smallest of the three in typical aquarium planning	Larger than Green Neon	Generally the largest of the three
Blue stripe	Extends strongly along most of the body	Prominent but paired with a larger posterior red area	Prominent above a long red lower stripe
Red marking	Restricted and comparatively subtle	Stronger on the rear lower body	Extends along much of the lower body
Planning emphasis	Very soft warm water, fine food and a calm small-fish community	Check the exact population and source conditions	Warm soft-water community with more adult space

The comparison is a practical identification guide, not a promise that every individual has textbook colour. Age, stress, lighting, health, camera processing and background can alter how stripes and red markings appear. Scientific identity should come from supplier provenance and product records, not from colour alone.

Breeding and sexing limits

Sex is not guaranteed at any offered size. Mature females may become fuller-bodied and males can appear slimmer, but this is not a reliable way to sex very small juveniles or to build a guaranteed pair. Ordering several fish creates a social group; it does not guarantee a chosen sex ratio or breeding outcome.

Published summaries describe the species as an egg scatterer that may spawn more successfully in a school than in a simple pair. Breeding attempts generally use a separate, very soft, acidic, dim aquarium with fine spawning material and suitably conditioned adults. Parents may eat eggs, and the resulting fry are extremely small. This makes breeding a specialist project rather than an automatic result of ordinary community care.

This listing does not promise an exact clutch size, hatch time, fertility rate or number of surviving fry. Those outcomes depend on the adults, water chemistry, microbial environment, food and breeder technique. Specialist sources and actual aquarium conditions are more useful than assuming one fixed spawning schedule.

Health observation and first days

Before purchase, prepare the complete aquarium and confirm the water is stable. On arrival, follow the current instructions supplied with the order and avoid sudden changes in temperature or chemistry. Keep lighting subdued during settling and make sure the chosen food is small enough. Do not add a new group to a tank already showing ammonia, nitrite, unexplained deaths or active disease.

Healthy settled fish should use the water column, respond to appropriate food and maintain a smooth body profile. The Merck Veterinary Manual's common signs of illness in fish includes appetite loss, breathing changes, spots, weight loss and abnormal swimming. Persistent isolation, clamped fins or repeated flashing also warrant investigation. None of those signs proves one diagnosis. Test water first, review the complete environment and seek qualified aquatic-veterinary advice when the problem is severe or persistent.

Do not medicate a display aquarium on guesswork. Merck's aquarium-fish management guidance discourages prophylactic medication without diagnostic testing and explains that treatment choice depends on the condition and delivery route. Treatments can affect filtration, plants, snails and shrimp, while incorrect dosing is particularly risky for tiny fish. If treatment is necessary, identify the problem as reliably as possible and follow the exact product instructions. Copper-containing products are hazardous to many invertebrates, so the whole aquarium population must be considered.

A separate quarantine system can reduce the chance of introducing disease, but it must be cycled, heated and suitable in its own right. Merck recommends at least 30 days for pet-fish quarantine and notes that longer may be necessary. Use separate equipment, observe feeding and behaviour, and investigate illness before transfer. Moving fish through an unstable container is not a safe substitute for a functioning quarantine aquarium.

About the gallery images

The four existing gallery files are representative illustrations. They show small blue-striped tetra-like fish in aquarium scenes and a clean side view, but they are not photographs of the exact fish dispatched and do not independently prove scientific identity. Colour, body condition, size and markings can differ from current live stock.

One gallery scene shows two fish. That image illustrates social context and does not change the sale unit: each selected quantity remains one unsexed fish. None of the images provides dependable scale for choosing a variant. Use the option selector for the purchased size band and contact the team before ordering when exact current-stock information is essential.

Delivery and ordering

Availability, dispatch days, delivery areas, courier arrangements and the process for reporting an arrival problem can change. Check the current delivery information before checkout. The linked delivery page contains the service terms that apply at the time of ordering.

Prepare the aquarium before ordering and arrange for the parcel to be brought indoors promptly. Do not leave live fish in a vehicle, exposed porch or parcel locker. If there is a delivery concern, retain the packaging, take clear evidence and follow the contact instructions in the current delivery policy.

Before choosing Green Neon Tetras

• Confirm that your aquarium can maintain stable 23-27 C, mildly acidic pH and very soft water.
• Plan a group of at least ten without exceeding the aquarium's mature capacity.
• Use about 60 litres and a 60 cm length as a conservative starting point, with more room for a community.
• Prepare gentle mature filtration, shaded planting, open midwater and a secure cover.
• Have genuinely fine prepared, frozen or live foods ready for the selected size.
• Choose only small peaceful companions with overlapping water requirements.
• Remember that one selected quantity is one unsexed fish, not a six-fish pack or a guaranteed pair.
• Treat the gallery as representative media rather than exact-stock photography.
• Read the current delivery information before ordering.

Green Neon Tetra is a strong choice for an aquarist who values a subtle natural display and is prepared to maintain soft-water stability. Its appeal comes from a healthy social group moving through a mature planted aquarium. Correct identity, suitable water, fine feeding, careful companion choice and enough group space matter most.