Gold Black Molly (Poecilia sphenops gold black molly)

Decide whether this molly suits your aquarium

The Gold Black Molly is a colour form of Poecilia sphenops, a livebearing freshwater fish in the poeciliid family. FishBase places the species in Central and South America, from Mexico to Colombia, and records a maximum length of 7.5 cm standard length. It suits a keeper prepared to provide hard, alkaline water, a planted and properly filtered aquarium, companionship and enough floor space for active adult fish.

Keep the aquarium at 21–28°C, pH 7.5–8.0 and 15–18 dGH. These routine targets sit within the ranges reported by FishBase and the Seriously Fish species profile, while also fitting OATA’s narrower upper pH and hardness guidance. Stable mineral content matters: Seriously Fish warns that soft or acidic conditions can weaken this fish and may be associated with shimmying, clamped fins or fungal problems.

Plan around a base measuring 90 × 30 cm and a volume of about 81 litres. That is the aquarium size presented by Seriously Fish for Poecilia sphenops. The footprint gives the fish useful horizontal swimming room, while the volume makes temperature and water quality easier to hold steady than they would be in a very small aquarium.

For social planning, OATA’s group guidance for guppies and mollies advises keeping at least three. Its suggested mixed-sex ratio is two females to each male, intended to reduce pressure on females and other inhabitants. Because this offer does not guarantee sex, build the group gradually, observe interactions and avoid assuming a particular ratio from colour or dispatch size.

Choose the dispatch grade and sold unit

One purchase supplies one Gold Black Molly. Use the live size selector to choose the labelled dispatch grade: 3–4 cm or XL. The 3–4 cm label is a measured dispatch range, while XL is the catalogue’s named grade and does not state a centimetre range. The size you select is the size supplied, not the adult size.

Plan the permanent aquarium around the recorded adult length of 7.5 cm standard length, the 90 × 30 cm base and the social group rather than around the fish’s dispatch grade. A smaller fish still needs a route into the full adult setup, and an XL label does not replace the adult-size guidance. When adding more than one fish, assess the aquarium’s existing occupants and biological capacity instead of multiplying dispatch lengths into a stocking rule.

Sex is guaranteed only when the selected option explicitly states male or female. This Gold Black Molly listing has no sex-guaranteed option.

Some gallery images have been digitally enhanced to improve image quality. They show the listed type of animal rather than guaranteeing the exact markings of the individual supplied, so natural colour and pattern can vary.

The gold-and-black pattern is the defining trade presentation of this fish, while individual colour placement and intensity can vary. Gallery scenes may show one or two fish for visual context; the purchase unit remains one animal. Browse the molly fish collection when comparing this colour form with other mollies, but assess every proposed fish against the same adult-space and water-chemistry requirements before combining them.

Before making the choice

• Measure the aquarium: use its base dimensions as well as its stated volume.
• Test the water: confirm that pH and hardness fall within the target range.
• Count the planned group: OATA advises at least three guppies or mollies for companionship.
• Read the grade literally: 3–4 cm is measured; XL is a named dispatch grade.
• Check every companion: peaceful behaviour alone is not enough if the fish need softer or more acidic water.

Hold hard, alkaline water steady

Keep this molly at 21–28°C, pH 7.5–8.0 and 15–18 dGH. The range is an overlap: FishBase reports 18–28°C, pH 7.5–8.2 and 11–30 dGH; Seriously Fish gives 21–28°C, pH 7.0–8.5 and 15–30 dGH; OATA gives 20–28°C, pH 7.0–8.0 and 8–18 dGH for guppies and mollies. Using the shared range respects the species’ hard-water needs without extending beyond any of those values.

Measure pH and general hardness before choosing the fish, then compare the result with the target. The aquarium water chemistry guide explains what the measurements mean, while the water matcher provides a practical comparison with the stated range. Test the aquarium itself rather than relying only on a regional water report, because aquarium materials, maintenance and biological activity can affect the result.

Do not use salt as a substitute for suitable hardness. Seriously Fish explains that calcium and magnesium are important to long-term health and says salt is not necessary. The practical decision is therefore to establish appropriate mineral hardness in the aquarium rather than treating salt as the answer to soft water.

If a fish begins shimmying, clamps its fins or loses its usual swimming control, test temperature, pH, hardness, ammonia and nitrite promptly. Correct the underlying water condition carefully and avoid abrupt swings. A result outside the target is a reason to stabilise the aquarium before adding further livestock.

Plan space around the adult fish

Use an aquarium with a 90 × 30 cm base and a volume of about 81 litres as the planning point for Poecilia sphenops. Volume supports dilution and stability, while the base dimensions define the horizontal room the fish can use. Check both figures: a tall aquarium may hold a similar number of litres without offering the same swimming footprint.

Prefer a planted layout with clear swimming space. Seriously Fish recommends a planted aquarium, and OATA advises plants, gravel or sand and suitable shelter for guppies and mollies. Arrange vegetation around the back and sides or in defined clumps so the fish can move between cover and open water. Dense planting can also help individuals break visual contact when social attention becomes persistent.

Build the layout in layers

• Base: use aquarium gravel or sand.
• Cover: provide live plants where practical; suitable artificial plants and ornaments can provide shelter when live plants are not used.
• Swimming room: retain an open route across the aquarium rather than filling the whole footprint with decoration.
• Safe edges: check ornaments and artificial plants for rough or sharp surfaces that could damage fins.
• Equipment access: leave enough room to inspect the filter and remove waste during water changes.

Judge capacity by the complete community, not by the molly group alone. More fish produce more waste and require more biological filtration. OATA advises increasing livestock numbers slowly so the filter’s beneficial bacterial population can adjust as feeding and waste increase. An aquarium that meets the basic footprint can still become overcrowded if numerous companions are added without allowing for their adult sizes.

Watch how the fish use the layout after introduction. Persistent crowding into one corner, repeated pursuit through a narrow gap or difficulty reaching food indicates that the arrangement needs attention. Move cover to create more than one retreat while preserving an open route, then observe whether movement becomes more balanced.

Establish filtration before adding fish

Run a properly established biological filter before adding the Gold Black Molly. The RSPCA’s aquarium guidance explains that fish release toxic ammonia and that beneficial bacteria in a working filter convert it first to nitrite and then to safer nitrate. Ammonia and nitrite must both test at 0 mg/l before introduction.

For an aquarium of about 81 litres, Seriously Fish presents a turnover of four to five times the aquarium volume per hour and gives a corresponding filter rating of 325–405 litres per hour. Treat that rating as a starting point for this aquarium size. Real flow through media can be influenced by blockage and maintenance, so inspect the system rather than relying only on the label.

Prepare and mature the aquarium before livestock arrives. The first tropical aquarium guide covers the preparation sequence. A heater holding the chosen point inside 21–28°C, a filter with established biological media and repeatable zero ammonia and nitrite results form the basic readiness check.

Use a three-part readiness test

1. Equipment: confirm that the filter is running continuously and the heater holds a steady temperature.
2. Water: test ammonia and nitrite and require 0 mg/l for both; also check pH and hardness against the molly range.
3. Capacity: consider the existing fish, their adult sizes and the extra waste created by another animal or group.

Add fish gradually. OATA warns that stocking too quickly can lead to new tank syndrome because the bacterial population may not yet process the increased waste. After an addition, continue testing rather than assuming the previous result still represents the aquarium under its new load.

If ammonia or nitrite becomes detectable, stop adding livestock, test again to confirm the result and address water quality. Reduced feeding may limit further waste while the immediate problem is handled, but it does not replace restoring effective biological filtration. Check for blocked flow and rinse filter media in water removed from the aquarium, never under the tap, to reduce damage to the beneficial bacteria.

Feed an omnivorous molly with variety

Feed once a day, offering only what the fish can finish within a few minutes. Remove or reduce any portion that remains uneaten, because decomposing food adds waste to the aquarium. This schedule follows OATA’s guidance for guppies and mollies; body condition, appetite and water tests show whether the portion is appropriate.

Build the staple around quality flake or granules with a strong algae or vegetable component. FishBase records adults eating worms, crustaceans, insects and plant matter and notes that aquarium fish graze green algae and accept dried food. Seriously Fish describes the species as omnivorous, feeding on zoobenthos and detritus in nature, and recommends including vegetable matter such as vegetable flake or blanched spinach.

Add small live or frozen foods for variety. OATA names daphnia, small bloodworm and tubifex for guppies and mollies. Match the item and portion to the fish’s mouth, and use variety as part of the diet rather than turning one rich food into every meal.

Observe every member of the group during feeding. One fish repeatedly missing meals may be stressed, unwell or excluded by a more assertive individual. Spread a modest portion across more than one point when that helps all fish reach food, but keep the total within the few-minute limit.

Use appetite as one observation alongside swimming, breathing, colour and body condition. A sudden reduction in feeding interest warrants a water test, because OATA lists reduced intake as a health warning. Check ammonia, nitrite, temperature, pH and hardness before changing the diet repeatedly. When the fish eat normally but uneaten food remains, the first correction is a smaller portion.

Build the social group carefully

Plan for at least three Gold Black Mollies or compatible guppies and mollies rather than keeping this fish alone. OATA recommends companionship for the group and suggests two females to each male when keeping mixed sexes. That ratio is intended to reduce stress caused by persistent male attention.

This offer does not guarantee sex, so do not buy a particular grade on the assumption that it represents a male or female. Seriously Fish notes that adult males are generally smaller, more colourful and possess a gonopodium, but visual characteristics in an image or a dispatch-size label do not determine what this offer supplies. Observe the group you receive and adjust future stocking only after assessing the actual fish and the aquarium’s capacity.

Separate three decisions

• Companionship: use OATA’s minimum group of at least three.
• Sex ratio: aim for two females to each male when the sexes can be identified in the aquarium.
• Capacity: add more fish only when the 90 × 30 cm footprint, filtration and water quality can support the full community.

Introduce additions slowly. Each extra fish increases waste and may change the group’s social pattern. Test ammonia and nitrite after additions and watch for sustained pursuit, one fish being repeatedly driven into cover, missed meals or damaged fins. A brief interaction is different from a repeated pattern that prevents normal feeding or swimming.

Dense areas of planting can interrupt pursuit and give fish a route away from attention. Keep several passages through the planting so one dominant individual cannot control the only route. If one fish remains isolated despite suitable water and adequate cover, review group composition, aquarium space and the behaviour of every companion.

Remember that mollies are livebearers. A mixed-sex group may produce young, so the potential population and resulting biological load belong in the stocking decision. Do not crowd the aquarium in anticipation of a fixed adult count; maintain stable water and make each addition according to the capacity present at that time.

Separate dispatch size from adult growth

Plan for 7.5 cm standard length as the recorded adult maximum. FishBase gives 7.5 cm standard length for male or unsexed Poecilia sphenops. Seriously Fish presents a slightly larger planning figure of 8 cm standard length; the care specification uses the FishBase figure consistently, while the 90 × 30 cm aquarium base remains the practical space guide.

The 3–4 cm grade and XL grade describe dispatch size, not maturity, sex or final dimensions. A fish sent at 3–4 cm still needs the adult aquarium plan. XL remains a named grade, so do not assign it a centimetre range or treat it as proof that the fish has finished growing.

Use the adult plan from the start

• Reserve the 90 × 30 cm base and about 81-litre volume for the permanent setup.
• Size the social group and companion community for adult fish.
• Maintain 21–28°C, pH 7.5–8.0 and 15–18 dGH throughout growth.
• Adjust food portions by appetite and body condition, while retaining the once-daily, few-minute limit.
• Reassess filtration whenever the fish or overall community grows.

Growth should prompt practical checks rather than repeated moves. Confirm that open swimming routes remain clear, all group members reach food and the filter continues to hold ammonia and nitrite at zero. If the community begins using all available space, do not solve the problem by adding more livestock.

Keep a repeatable weekly routine

Change 25% of the aquarium water at least once a week. OATA strongly recommends this routine for guppies and mollies and advises using a siphon to remove solid waste from the substrate. Treat replacement tap water with conditioner before it enters the aquarium so chlorine or chloramine does not harm fish or filter bacteria.

Test the water at least weekly and record temperature, pH, hardness, ammonia and nitrite. Ammonia and nitrite must remain at 0 mg/l. OATA also advises keeping nitrate no more than 20 mg/l above the normal tap-water level. A written sequence of results is more useful than a single test because it can reveal gradual change before fish behaviour becomes visibly abnormal.

Weekly checklist

1. Observe swimming, breathing, colour, fins, scales, body condition and appetite before disturbing the aquarium.
2. Test water and compare the result with the established target and previous readings.
3. Remove 25% of the water while siphoning accessible waste from the substrate.
4. Treat replacement water with tap-water conditioner and bring it back carefully without causing an abrupt change.
5. Check the filter intake and flow for blockages.
6. Rinse filter media lightly in removed aquarium water only when cleaning is needed.

Rinse filter media in water removed from the aquarium, never under the tap. Chlorine or chloramine may damage the bacterial population that processes ammonia and nitrite.

Respond to trends early. Faster breathing, hanging at the surface, sitting on the bottom, erratic swimming, unusual hiding, colour change, white spots, fluffy growths, damaged fins, altered body condition or reduced feeding interest all justify an immediate water test. If the values are outside the target, correct the aquarium carefully and pause further stocking.

Contact us when health changes continue after the water has been tested and stabilised. Share the measured values and describe the change in swimming, breathing, appearance or feeding so the next decision can be based on the fish’s condition and aquarium environment.

Follow the arrival and acclimatisation steps

Arrange for someone to receive the parcel because live fish must not be left unattended. Tropical Fish Co hand-bags fish in pure oxygen, uses an insulated poly box and adds a heat pack when the weather calls for it. A licensed live-animal courier carries the parcel, with tracking and the confirmed delivery date sent by email.

Read the current delivery and Live Arrival Guarantee policy before the journey.

Follow the arrival sequence

1. If practical, start filming before the parcel is opened, showing the parcel still sealed and the outer box visible.
2. Open the parcel in one continuous take and show the fish still inside the bag before anything is disturbed.
3. Float the bag in the prepared aquarium for 20–30 minutes.
4. Release the fish after this acclimatisation period without pouring the bag water into the aquarium.

Prepare the receiving aquarium before the parcel arrives. OATA’s group guidance advises checking that ammonia and nitrite are both 0 mg/l before adding fish. Temperature should already be stable within 21–28°C, pH should be 7.5–8.0 and hardness should be 15–18 dGH. Confirm that the filter is operating and that suitable cover and open swimming space are in place.

Once released, watch breathing, swimming posture and the way the fish uses cover. OATA advises monitoring newly introduced fish for normal swimming, colour, temperament, breathing, physical condition and feeding. Test the water if the fish hangs at the surface, sits on the bottom, swims erratically or shows a marked change in breathing.

First-week checkpoints

• First observation: confirm that the fish can maintain its position and move around the aquarium.
• First feeding: check that it notices food and can reach a modest share without persistent pursuit.
• Daily check: look for clamped or damaged fins, colour change, unusual hiding or altered breathing.
• Water check: test ammonia and nitrite after the addition because the biological load has increased.
• Community check: intervene if repeated chasing prevents normal feeding or access to open water.

Screen every companion for the same water

Choose peaceful companions that thrive at 21–28°C, pH 7.5–8.0 and 15–18 dGH. Seriously Fish describes Poecilia sphenops as peaceful but advises keeping it only with fish able to tolerate the same conditions. That water requirement is why this molly should not be treated as an automatic fit for every general community.

Named possibilities include other Poecilia, some rainbowfish, and hard-water-tolerant barbs and tetras. These are categories for screening, not universal approvals. Check the proposed species’ adult size, temperament and full water range, then confirm that its needs overlap the molly target without forcing either fish to the edge of its requirements.

Avoid fish whose health depends on soft or acidic water, because the molly’s required hard, basic conditions would create a direct conflict. Seriously Fish also advises keeping Poecilia sphenops and Poecilia latipinna separately when the aim is to prevent interbreeding.

Invertebrate compatibility requires an individual assessment of the proposed animal’s water needs and interactions. Use the same test: shared temperature, pH and hardness, enough space, and behaviour that does not prevent either animal from feeding or using cover. Contact us for a stocking assessment when you can provide the aquarium dimensions, measured water values, filtration and the exact animals already present.

Compatibility remains a continuing decision after introduction. Water chemistry may align while social behaviour does not. Provide cover, retain open swimming routes and watch whether every fish feeds and moves normally.

Act on repeated chasing or stress

Observe the community closely during the first week after introduction. Look for repeated chasing, one fish being driven into cover, blocked access to food, clamped or damaged fins, unusual hiding, erratic swimming or a clear change in breathing. A pattern that interferes with feeding or normal movement needs action.

Start with water tests because poor conditions can change behaviour and weaken fish. Confirm 21–28°C, pH 7.5–8.0, 15–18 dGH, 0 mg/l ammonia and 0 mg/l nitrite. If a result is outside the target, stabilise it carefully and pause any further additions. Do not interpret shimmying as normal molly behaviour; Seriously Fish associates it with unsuitable soft or acidic conditions.

Match the response to what you see

• One fish cannot reach food: offer the modest portion across more than one point and check whether pursuit still prevents access.
• Chasing follows one route: rearrange planting to break the line of sight and create more than one passage.
• A fish remains hidden: check water first, then assess whether the group composition or a companion is applying persistent pressure.
• Fins become clamped: test pH, hardness, ammonia and nitrite promptly and inspect for repeated social stress.
• Breathing changes: check water quality and filter operation without delay.

Do not add more fish merely to distract an aggressor. Every addition raises the biological load and can make the social pattern more complicated. First confirm that the aquarium is large enough, the filter is coping and the layout provides cover without sacrificing swimming room.

Review the group ratio when the sexes can be identified in the aquarium. OATA’s two-females-to-one-male suggestion is intended to reduce persistent pressure in mixed-sex groups, but the aquarium still needs room and filtration for every fish. Any adjustment must therefore satisfy social and biological capacity together.

Get answers to common Gold Black Molly questions

How big does a Gold Black Molly get?

It reaches a recorded maximum of 7.5 cm standard length, so plan its aquarium and community around that adult figure rather than its dispatch grade.

What size aquarium does a Gold Black Molly need?

Plan on a 90 × 30 cm base and about 81 litres, using a planted, properly filtered setup with open swimming room and enough capacity for the whole social group.

How many Gold Black Mollies should I keep together?

OATA’s guppy-and-molly guidance advises at least three and suggests two females to each male for a mixed-sex group, although this offer does not guarantee sex.

Is this fish suitable for a beginner?

A beginner should choose it only after confirming a mature filtered aquarium around 81 litres, the FishBase, Seriously Fish and OATA overlap of 21–28°C, pH 7.5–8.0 and 15–18 dGH, and a plan for at least three fish.

What does a Gold Black Molly eat?

Feed quality flake or granules with a high algae content once daily in an amount eaten within a few minutes, adding vegetable matter and small live or frozen foods such as daphnia, bloodworm or tubifex for variety.

What temperature and pH does a Gold Black Molly need?

Keep it within the FishBase, Seriously Fish and OATA overlap of 21–28°C, pH 7.5–8.0 and 15–18 dGH to provide hard, alkaline aquarium water.

Is this fish aggressive or likely to nip fins?

Seriously Fish describes the Gold Black Molly as peaceful; choose companions sharing its hard-water conditions and monitor repeated chasing, blocked feeding or fin damage after introduction.

Which fish can live with it?

Seriously Fish names other Poecilia, some rainbowfish, and hard-water-tolerant barbs and tetras; screen each proposed species against the FishBase, Seriously Fish and OATA overlap of 21–28°C, pH 7.5–8.0 and 15–18 dGH, as well as adult space and peaceful behaviour.

How does this fish arrive alive in the UK?

If practical, film the sealed parcel before opening it, then continue in one continuous unboxing video showing the fish inside the bag before anything is disturbed. Tropical Fish Co hand-bags it in pure oxygen, uses an insulated poly box and a heat pack when weather calls for one, and uses a licensed live-animal courier; someone must receive it, then float the bag for 20–30 minutes before release without pouring bag water into the aquarium. We strongly recommend an unboxing video when practical: it helps us investigate arrival concerns faster, resolve them with less back-and-forth and understand packing or transit issues so we can reduce recurrence. Video is optional and clear photos are accepted. Never delay necessary animal care to record evidence.

Read the care and identity references

• FishBase: Poecilia sphenops — scientific identity, family, distribution, environmental range, diet and recorded maximum length.
• Seriously Fish: Poecilia sphenops — aquarium dimensions, water conditions, diet, behaviour and compatibility.
• OATA: How to look after guppies and mollies — group care, companionship, feeding, maintenance and observation.
• RSPCA aquarium environment guidance — biological filtration and aquarium waste processing.
• Tropical Fish Co delivery and Live Arrival Guarantee policy — packing, receipt, acclimatisation and claim procedure.