Neon Dwarf Rainbowfish (Melanotaenia praecox)

Choose an active, peaceful shoal

The Neon Dwarf Rainbowfish (Melanotaenia praecox) is a freshwater member of the rainbowfish family Melanotaeniidae from the Mamberamo River in northern Irian Jaya, Indonesia. It reaches 5 cm standard length and suits a keeper who wants an active, peaceful shoal in a planted community aquarium. We rate its care level as easy for a prepared beginner who can provide a mature filter, stable water and consistent maintenance.

FishBase records its identity, family and Mamberamo River distribution. Seriously Fish describes it as very peaceful, active and best kept in a shoal of at least 6–8, preferably more.

Plan around the decisive numbers

• Group: Keep at least six together; eight or more is preferable.
• Water: Keep 23–27°C, pH 6.8–7.5 and 5–12 dGH. These are the overlap of Seriously Fish species guidance and OATA rainbowfish guidance.
• Space: Plan for an aquarium at least 80 cm long and no less than about 54 litres, with a base of at least 60 × 30 cm.
• Layout: Combine dense planting and floating cover with clear swimming lanes.

Choose the dispatch size for one fish

One purchase supplies one Neon Dwarf Rainbowfish from the selected size. Use the live size selector to choose from the labels 2 - 2,5 cm, 2,7 - 3,3 cm, 3,5 - 4 cm, 4-5 cm and XL. The size you select is the size supplied, not the adult size. Plan the aquarium and its companions around the 5 cm adult length rather than the dispatch measurement.

The numeric labels describe the fish's dispatch size. XL is a named grade without a fixed centimetre measurement, so use the label as shown and do not convert it into an assumed length. If you are building the minimum shoal from this offer, set the purchase quantity to at least six animals and check that the aquarium already has the space and biological capacity for the complete group.

Sex is guaranteed only when the selected option explicitly states male or female. This Neon Dwarf Rainbowfish listing has no sex-guaranteed option.

The gallery images are representative, based on reference photographs of this species, so colours can look slightly different from the live animal.

Make the size decision in the right order

1. Confirm that the mature aquarium is at least 80 cm long and can house the full shoal.
2. Check that its routine water remains within 23–27°C, pH 6.8–7.5 and 5–12 dGH.
3. Choose the dispatch label on the live selector.
4. Set the quantity for the group you intend to keep, remembering that each purchase unit is one fish.

To compare this fish with other members of the family, browse the rainbowfish collection. Compare adult dimensions, activity, group requirements and water needs before choosing between species.

Plan the aquarium around the adult length

Plan for an adult length of 5 cm standard length, the maximum length FishBase records. Seriously Fish gives a larger length of 8 cm standard length and describes the fish as active despite its small size.

Provide an aquarium at least 80 cm long. FishBase gives 80 cm as the minimum aquarium length, while Seriously Fish gives a minimum base of 60 × 30 cm, a height of 30 cm and a volume of about 54 litres. Meet both recommendations by choosing at least 80 cm of length without dropping below a 60 × 30 cm base or about 54 litres.

Check length, base and volume together

A volume figure alone can hide an unsuitable shape. A tall aquarium may contain 54 litres yet offer less horizontal swimming room than this active shoal needs. Start with the 80 cm length, then confirm that the base is at least 60 × 30 cm and that the filled aquarium provides no less than about 54 litres.

Group size changes the practical space decision. Six fish form the minimum shoal recommended for this species, while eight or more is preferable. The minimum dimensions are a starting point for a modest group, not permission to add fish without checking the aquarium's swimming room and biological capacity.

Measure usable swimming room after wood, rocks, plants and equipment are installed. Preserve open horizontal lanes between planted areas so the shoal can move through the aquarium rather than being confined to a small open corner.

Hold a stable routine water range

Keep the aquarium at 23–27°C, pH 6.8–7.5 and 5–12 dGH. The temperature is the overlap of FishBase's recorded 22–28°C environment, Seriously Fish's 23–28°C aquarium range and OATA's 22–27°C rainbowfish guidance. The pH and general hardness values are the overlap of Seriously Fish's 6.8–7.5 and 5–15 dGH ranges with OATA's 6.5–8.0 and 4–12 dGH ranges.

Aim for ammonia at 0 mg/l and nitrite at 0 mg/l. OATA also advises keeping nitrate no more than 20 mg/l above the normal tap-water level. These waste readings matter because rainbowfish can be stressed by even small amounts of ammonia and nitrite.

Use measurements to make each decision

• Before adding the shoal: Confirm that ammonia and nitrite are both zero and that temperature, pH and hardness sit inside the routine ranges.
• Every week: Test ammonia and nitrite at least once, then record the result so gradual changes are visible.
• Before a water change: Check that replacement water is treated with tap-water conditioner to remove chlorine or chloramine.
• After an unexpected behaviour change: Test the water before assuming the cause is social or health-related.

Use our water chemistry guide to understand what each measurement means. Enter measured values into the water matcher when comparing an established aquarium with the routine range.

Do not chase a target by making abrupt changes. Choose an aquarium whose normal water can be maintained consistently inside the range, then use regular testing and partial water changes to detect drift. The larger the aquarium, the more stable its temperature and water quality will be, but whatever its size it still needs a working filter and scheduled maintenance.

Combine planted cover with open swimming space

Use a heavily planted aquarium while preserving broad, open areas for swimming. Seriously Fish recommends dense planting for this species and notes that it shows its best colours in that setting. Separate planted zones with clear horizontal lanes so the shoal can swim and display without plants filling the entire aquarium.

Diffuse bright light with floating plants. The fish does not appreciate bright conditions, and floating cover softens light while leaving the lower planting visible. Position that cover so it does not remove every open lane at the surface or cast the whole aquarium into one dense block of shade.

Build the layout from the outside in

1. Mark out an open route that runs along the 80 cm aquarium length.
2. Place taller or denser planting around that route rather than through its centre.
3. Add floating plants to diffuse incoming light.
4. Use aquarium gravel or sand as the substrate.
5. Recheck the open route after plants, ornaments and equipment are in place.

OATA recommends gravel or sand and live plants to provide cover for rainbowfish. Suitable ornaments can add shelter when live planting is limited, but they should not replace the open space this active species needs. Avoid creating narrow dead ends where the shoal has to turn repeatedly around bulky décor.

The best layout balances two needs rather than maximising only one. Plant cover gives visual shelter and softer conditions; open water provides room for active movement and display. A densely planted back and side area with open space through the middle is one workable arrangement, provided the final swimming lane remains broad and continuous.

Watch how the complete shoal uses the aquarium. If fish repeatedly crowd into one small open patch, thin or move plants and ornaments to restore a longer route without removing all cover.

Run and maintain the biological filter

Use a mature, working biological filter at all times. The RSPCA explains that biological filtration supports beneficial bacteria which convert toxic ammonia first into toxic nitrite and then into safer nitrate. The filter must be established before the fish are added and maintained without destroying that bacterial population.

For an aquarium of about 54 litres, Seriously Fish gives a turnover of four to five times the aquarium volume each hour. That corresponds to a filter rated at approximately 215–270 litres per hour for that volume. If the aquarium is larger, apply the four-to-five-times turnover to its actual volume rather than reusing the 54-litre example.

Follow a weekly maintenance rhythm

1. At least once every week, change 25% of the aquarium water.
2. Use a siphon to remove solid waste from the substrate where necessary.
3. Treat replacement tap water with conditioner before it enters the aquarium.
4. Test ammonia and nitrite at least once per week.
5. Check the filter for blockages and confirm that water is moving normally.

Change 25% of the aquarium water at least once every week.

When filter media needs cleaning, rinse it lightly in aquarium water removed during the partial water change. Do not rinse it under the tap. Chlorine or chloramine may kill beneficial bacteria established in the media and reduce the filter's ability to process fish waste.

Never treat clear-looking water as proof that the biological filter is coping. Use test results, normal flow and the fish's behaviour together when judging aquarium stability.

Feed a varied omnivore diet once daily

Feed a good-quality flake or granule as the regular dried food, supported by suitably small live or frozen foods. Seriously Fish describes this species as an unfussy omnivore that will accept most dried, frozen and live foods. OATA recommends a good-quality flake or granule for rainbowfish and says they will also benefit from small live or frozen foods such as daphnia, small bloodworm or tubifex.

Feed once a day and offer only what the shoal can eat within a few minutes. Start with a restrained portion, watch the whole group feed, and stop adding food when interest falls. This approach is more reliable than using a fixed pinch for every aquarium because group size and food format differ.

Use variety without increasing the total portion

• Regular dried food: Use a quality flake or granule suitable for the fishes' mouths.
• Live or frozen variety: Rotate small daphnia, bloodworm or tubifex through the feeding plan.
• Portion control: Keep the total feeding period within a few minutes once daily.
• Observation: Check that active fish are not taking every item before quieter group members feed.

Regular feeds of live food will help the fish show their best colours, but they remain part of a varied diet rather than a reason to increase the daily amount. Substitute them for part of the normal portion instead of adding a second full meal.

Overfeeding leaves uneaten food to break down and release waste into the water. If food remains after the group has stopped feeding, reduce the next portion and test water quality if the aquarium becomes cloudy or the fish behave differently.

Keep feeding consistent enough to judge changes in appetite. A sudden reduction in food intake is easier to recognise when the type, timing and portion have not been changing unpredictably.

Acclimatise with the store procedure

Prepare the mature aquarium before the parcel arrives, then follow the store procedure in order. The temperature, pH and hardness should already sit within the routine range, with ammonia and nitrite at zero. Do not use arrival day to make major changes to the aquarium layout or biological filter.

Follow these arrival steps

1. Be present to receive the parcel so live fish are not left unattended.
2. Start a continuous unboxing video before opening the parcel, with the sealed parcel and outer box visible.
3. Open and inspect the parcel on the same day in one continuous take, showing the fish inside the sealed bag before anything is disturbed.
4. Float the bag for 20–30 minutes before releasing the fish.
5. Release the fish without pouring the bag water into the aquarium.

Filming from the sealed parcel onward preserves the complete sequence needed for a Live Arrival Guarantee claim. Keep the order number with the video. If anything is wrong, contact us the same day with both items so the concern can be assessed promptly.

Read the current delivery and Live Arrival Guarantee policy before the delivery date. The policy explains that fish are hand-packed in pure oxygen inside an insulated box, with a heat pack when the weather calls for it, and carried by a licensed live-animal courier.

Keep the bag sealed while recording the condition of the fish, then complete the release without transferring transport water into the aquarium. Before the parcel arrives, the aquarium must already have the correct water values and a mature filter.

Add the shoal without overloading the filter

Add fish only to a mature aquarium with ammonia and nitrite at zero. Beneficial bacteria in the filter must process the extra waste created whenever fish numbers and feeding increase. Prepare and mature a first aquarium with our first tropical tank guide before arranging livestock.

Increase the aquarium population slowly. OATA warns that overstocking, or stocking the aquarium too quickly, can cause new tank syndrome because there may not yet be enough beneficial bacteria to process the added waste. This listing is for a shoaling species, so reconcile gradual stocking with the need for an appropriate group by establishing enough biological capacity before the first group is introduced.

Use first-week checkpoints

• Before introduction: Confirm 23–27°C, pH 6.8–7.5, 5–12 dGH, ammonia at zero and nitrite at zero.
• At feeding: Check that the group approaches food and that each fish has an opportunity to eat.
• During swimming: Look for normal use of open water rather than persistent surface hanging, bottom sitting or erratic movement.
• At the weekly check: Test ammonia and nitrite, inspect filter flow and carry out the scheduled 25% partial water change.

Do not add another species merely because the first group appears calm on the first day. Allow the filter load and behaviour to settle, then use water tests and the space remaining in the aquarium to decide whether any further stocking is appropriate.

Keep notes on temperature, pH, hardness, ammonia and nitrite alongside feeding and behaviour. A simple record distinguishes a one-off observation from a developing pattern and shows whether a change followed feeding, maintenance or additional livestock.

Act on health and behaviour changes

Learn the group's normal swimming, colour, breathing and appetite so changes stand out. Healthy fish should have clear, bright eyes, intact scales and undamaged fins, with swimming and feeding behaviour appropriate to the shoal.

Test water quality first when behaviour or appearance changes. Ammonia and nitrite must remain at zero, and the routine temperature, pH and hardness should remain within range. A water test gives an immediate action point without guessing at a disease or applying a treatment that may not fit the problem.

Match each observation to a first response

Look at the whole shoal as well as the individual fish. If several fish change at the same time, examine shared factors such as water quality, filter performance, feeding and a recent stocking change. If one fish changes, still test the shared water before moving to an individual assessment.

Keep portions controlled when appetite changes, and check that every fish can reach food if one loses condition. Continue controlled portions, remove the cause of any water-quality problem and document what the fish is doing. Extra uneaten food increases waste and can make the aquarium less stable.

If you are concerned about a fish's health, test the water and contact us for further guidance. Provide the measured values, aquarium dimensions, group size, companions, recent additions and a clear description of the change so the next decision is based on the aquarium as it is operating.

Keep a complete social group

Keep at least six Neon Dwarf Rainbowfish together, with eight or more preferable. Seriously Fish recommends a shoal of at least 6–8 and notes that the species can be skittish and does far better when kept in a shoal. FishBase gives five or more as an aquarium group and OATA at least five for rainbowfish generally, but plan for Seriously Fish's species recommendation of at least six.

The group is part of the compatibility plan, not an optional addition after other fish have filled the aquarium. Reserve adult swimming space and biological capacity for the complete shoal before choosing companion species. One fish per purchase means a planned minimum group requires a quantity of at least six.

Plan the shoal before the community

1. Choose an aquarium at least 80 cm long and no less than about 54 litres.
2. Reserve open horizontal swimming lanes for the rainbowfish group.
3. Allocate capacity for at least six adults at 5 cm standard length.
4. Add companion species only after their adult size, activity and water needs have been screened.

More than six can provide a stronger social group when aquarium space and filtration support it. A larger shoal still needs the aquarium to provide open room and keep ammonia and nitrite at zero.

Conspecific company also encourages males to display their colours. Treat that as a group behaviour rather than a way to identify or guarantee the sex of an individual fish. Build the purchase decision around shoal size, adult dimensions and aquarium capacity.

Screen every community companion

Choose similarly sized, non-timid fish whose routine water needs overlap 23–27°C, pH 6.8–7.5 and 5–12 dGH. Seriously Fish describes the Neon Dwarf Rainbowfish as very peaceful and names similarly sized rainbowfish, characins, danios, barbs, dwarf cichlids, freshwater gobies and Corydoras as good community candidates.

These names are starting points rather than universal approvals. Check the proposed species at its adult size, compare its activity with an active rainbowfish shoal, and confirm that both can share the same water range and aquarium layout. The aquarium must also retain enough swimming room and filtration capacity for every adult animal.

Use a clear screening rule

OATA advises that active rainbowfish should not be mixed with fish that are timid or much smaller. Avoid those combinations rather than assuming extra planting will make the mismatch safe. Cover can help a fish use the aquarium, but it does not change the adult size or activity of either species.

Observe the community at feeding time and while the shoal crosses open water. Check whether every species can reach food, hold its normal position and use its preferred area without persistent hiding or damaged fins. A peaceful species description does not remove the need to watch the actual aquarium.

For a stocking and compatibility assessment, ask us with the aquarium dimensions, measured water values, filter details, current group sizes and the exact species being considered. That allows the decision to account for adult animals and the complete community rather than comparing common names alone.

Answer common keeper questions

How big does a Neon Dwarf Rainbowfish get?

It reaches 5 cm standard length. Use that adult figure when planning aquarium space and companions, even when choosing a smaller dispatch size.

What size aquarium does this fish need?

Use an aquarium at least 80 cm long and no less than about 54 litres, with a base of at least 60 × 30 cm. FishBase gives the 80 cm minimum length, while Seriously Fish gives the 60 × 30 × 30 cm and approximately 54-litre minimum.

How many Neon Dwarf Rainbowfish should I keep together?

Keep at least six, preferably eight or more. Seriously Fish recommends a shoal of at least 6–8 and notes that the species does far better when kept in a shoal.

Does this fish suit beginners?

We rate it easy for a prepared beginner. OATA describes rainbowfish as usually easy to keep, while this species still needs a mature filter, stable water, a full shoal and consistently high water quality.

What does a Neon Dwarf Rainbowfish eat?

Feed a quality flake or granule with small live or frozen foods such as daphnia, small bloodworm or tubifex for variety. Feed once daily and offer only what the shoal can eat within a few minutes.

What temperature and pH does this fish need?

Keep 23–27°C, pH 6.8–7.5 and 5–12 dGH. These routine values are the overlap of Seriously Fish species guidance and OATA rainbowfish guidance.

Is a Neon Dwarf Rainbowfish aggressive or likely to nip fins?

Seriously Fish describes it as very peaceful. Keep a proper shoal, choose similarly sized and non-timid companions, and monitor behaviour and fin condition whenever the community changes.

Which kinds of animals can this fish live with?

Consider similarly sized rainbowfish, characins, danios, barbs, dwarf cichlids, freshwater gobies and Corydoras after checking adult size, activity, group needs and water. Avoid timid fish and fish much smaller than the rainbowfish.

How does a Neon Dwarf Rainbowfish arrive alive in the UK?

Be present to receive the parcel, start a continuous unboxing video while the parcel is still sealed, open and inspect it the same day, and float the bag for 20–30 minutes before releasing the fish without pouring the bag water into the aquarium. Tropical Fish Co hand-packs fish in pure oxygen inside an insulated box, with a heat pack when the weather calls for it, for carriage by a licensed live-animal courier.

Check the public references

• FishBase: Scientific identity, family, distribution, recorded environmental temperature, length and aquarium group and length notes.
• Seriously Fish: Adult planning length, aquarium dimensions, water, layout, filtration, diet, behaviour and community guidance.
• OATA: Rainbowfish water, feeding, maintenance, introduction, welfare and compatibility guidance.
• RSPCA: Biological filtration and aquarium waste processing.
• Tropical Fish Co delivery policy: Packing, receipt, filming, acclimatisation and Live Arrival Guarantee procedure.