Lyra Molly Black (Poecilia sphenops lyra molly)

Choose a hard-water livebearer with defined space needs

The Lyra Molly Black (Poecilia sphenops) is a freshwater poeciliid from Central and South America, with a native range from Mexico to Colombia. FishBase records a maximum adult size of 7.5 cm standard length. It suits keepers who can provide a mature, filtered aquarium with hard, alkaline water and enough room for a small group.

The black designation identifies the colour form, while “lyra molly” identifies the lyretail form within the aquarium trade. Plan care around Poecilia sphenops: this is a peaceful livebearer, but it is not a general-purpose choice for every tropical community. Its companions must tolerate the same mineral-rich water.

Natural diet records describe adults eating worms, crustaceans, insects and plant matter. In aquariums, they also graze green algae and accept dried food. That mixed diet calls for both vegetable matter and suitable animal-based foods rather than a single, unvaried product.

Who it suits

OATA describes guppies and mollies generally as easy to keep. For this molly, success still depends on testing the water before purchase, using an adequately sized aquarium and maintaining the filter consistently. Soft or acidic conditions are a poor match even when the aquarium is otherwise established.

Check the decisive care numbers before choosing

Keep the aquarium at 21–28°C, pH 7.5–8.0 and 15–18 dGH. These routine targets are the overlap of FishBase’s recorded environmental range, Seriously Fish’s species aquarium guidance and OATA’s guppy-and-molly group guidance. They provide a practical hard, alkaline range rather than a species-specific optimum.

Seriously Fish uses an aquarium with a 90 × 30 cm base and approximately 81 litres for this species. Treat those dimensions as the starting point for the group, not as permission to fill every part of the aquarium with fish. Additional groups require more volume, while plants, shelter and open swimming room all need usable space.

OATA suggests keeping at least three guppies or mollies together because they require companionship. Its suggested ratio is two females to each male. This offer does not guarantee sex, so plan the group and aquarium capacity without assuming a particular ratio from colour, size or an illustration.

Understand the fish, size choice and gallery

One purchase supplies one Lyra Molly Black from the size selected on the live selector. Choose either 3.5-5 cm or XL as the dispatch grade. The size you select is the size supplied, not the adult size. Use the adult planning figure of 7.5 cm when choosing the aquarium, filter and group capacity.

Sex is guaranteed only when the selected option explicitly states male or female. This Lyra Molly Black 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 product identity, rather than an illustrated fish’s visible colour or body details, defines the black lyra form offered here. Each purchase adds one fish to the aquarium, so a keeper following OATA’s suggested group number must account for fish already present and the number being added.

For other forms within the same broad retail group, browse the molly fish collection. Compare each animal’s own adult size, water requirements and compatibility rather than assuming that every molly has identical needs.

Plan the aquarium around the adult size

Use 7.5 cm as the adult planning length for the Lyra Molly Black. FishBase records that maximum standard length for Poecilia sphenops. Seriously Fish lists 8 cm standard length, so its 90 × 30 cm base and approximately 81-litre aquarium remain the more spacious practical plan.

The 3.5-5 cm label describes the fish at dispatch. XL is also a dispatch grade and should not be converted into a different adult size. A smaller fish still needs an aquarium chosen for its adult body, its companions and the waste produced by the complete group.

Use the footprint as well as the volume

Start with a base measuring 90 × 30 cm and a volume of approximately 81 litres. A long, usable base lets the group move between planted cover and open water. Do not judge suitability from litres alone if the aquarium’s footprint is substantially different from the profile dimensions.

OATA notes that larger aquariums provide more stable temperature and water quality. It also advises increasing aquarium volume as more groups are added. Before adding fish, count every existing animal and consider the adult group rather than treating the new molly’s dispatch length as spare capacity.

Match equipment to the aquarium

For an aquarium around 81 litres, Seriously Fish uses a turnover of four to five times the aquarium volume per hour and points to a filter rated at 325–405 litres per hour. Its heater estimate is 75–100 W for holding 21–28°C when the room is around 20°C. Match the equipment to the aquarium’s actual volume while keeping the target temperature stable.

Work through a capacity check

Begin with the complete adult stocking plan, not the number of fish being added today. List the mollies already present, add one animal for each purchase and include every other resident at its own adult size. Then compare the finished plan with the 90 × 30 cm base, approximately 81-litre reference and the space required for planting and open swimming. If adding another group would crowd that footprint, use a larger aquarium rather than relying on the small dispatch length.

Check the equipment against the same finished plan. An aquarium near 81 litres can use the 325–405 litres-per-hour reference, but the filter still needs room to hold mature biological media and must remain unobstructed. The heater must hold the measured water between 21°C and 28°C; its dial setting alone is not the result. Confirm the temperature with a thermometer after the aquarium has stabilised.

Hold the water inside the shared hard-water range

Keep the Lyra Molly Black at 21–28°C, pH 7.5–8.0 and 15–18 dGH. This range lies within FishBase’s recorded conditions, Seriously Fish’s aquarium range and OATA’s guppy-and-molly range. Use measured values rather than relying on the words “hard water” alone.

The pH and hardness targets matter together. Seriously Fish warns that this species weakens rapidly in soft or acidic water, with shimmying, fungus or clamped fins among the possible signs. Test both the aquarium and the replacement water so a water change does not create a sudden move away from the established conditions.

Salt is not necessary for routine maintenance. Seriously Fish identifies calcium and magnesium—the minerals behind hard water—as important to long-term health. FishBase records the species from freshwater and brackish environments, but that natural occurrence is not an instruction to add salt to the aquarium.

Make a measured decision

A result of 25°C, pH 7.8 and 16 dGH sits inside all three routine targets. A result of pH 6.8 or 8 dGH falls outside this plan even if the temperature is suitable. Use our water chemistry guide to understand the tests, then enter the actual readings in the water matcher before deciding whether this fish fits the aquarium.

Read combinations, not isolated results

A temperature of 25°C does not make an aquarium suitable when its pH is 6.8, and a pH of 7.8 does not compensate for general hardness of 8 dGH. Compare every result with its own target. The aquarium fits this plan only when temperature, pH and hardness all sit inside the stated ranges and ammonia and nitrite both remain at 0 mg/l.

Check the replacement water before a partial change as well as the aquarium itself. If the aquarium reads pH 7.8 and 16 dGH, replacement water far outside those values can move the established conditions away from the target. Treat it with conditioner before use, then continue regular testing so gradual changes are seen before the fish shows altered behaviour or appearance.

Build a planted aquarium around a mature filter

Use a mature aquarium with a well-established biological filter. The RSPCA explains that fish release toxic ammonia and that filter bacteria convert it first to nitrite and then to the safer nitrate. A filter is therefore part of the animal’s life-support system, not simply a way to keep the water looking clear.

Seriously Fish prefers a planted aquarium for Poecilia sphenops. OATA also recommends live plants for cover, with plastic plants and suitable ornaments as alternatives when live planting is not used. Aquarium gravel or sand can be used as the substrate. Arrange the aquarium so the fish have both cover and unobstructed room to swim.

Prepare before adding livestock

Mature the filter and confirm that ammonia and nitrite are both 0 mg/l before adding the fish. Our first tropical tank guide explains how to prepare and mature an aquarium before livestock arrives. A running filter is not necessarily a mature filter; the important function is an established bacterial population capable of processing the fish’s waste.

Add fish gradually. OATA warns that stocking too quickly can exceed the capacity of the nitrifying bacteria, causing new tank syndrome and unhealthy ammonia or nitrite. Pause further additions whenever either compound is detectable and restore stable readings before reconsidering the stocking plan.

Keep the equipment working

Check the filter for blockages as part of routine maintenance. For an aquarium around 81 litres, use the 325–405 litres-per-hour filter range as a practical reference. Confirm the aquarium temperature with a thermometer rather than relying only on the heater setting, and keep it within 21–28°C.

Use three readiness checkpoints

• Water checkpoint: ammonia and nitrite must both read 0 mg/l, while temperature, pH and hardness must fit the stated ranges.
• Filter checkpoint: water must move through an established biological filter without a blockage restricting its operation.
• Layout checkpoint: plants or suitable ornaments must provide cover without removing the open swimming area from the 90 × 30 cm footprint.

Passing one checkpoint does not replace the others. Clear water can still contain ammonia or have unsuitable hardness, and a correctly sized aquarium can still be unsafe when its filter bacteria need individual assessment. Complete all three checks before the fish is introduced, then make further additions gradually so the biological filter can respond to the extra waste.

Feed an omnivorous diet with plenty of vegetable matter

Feed a varied omnivorous diet in one modest daily meal. OATA advises offering only what the fish can eat within a few minutes once a day. Remove the assumption that more food produces faster healthy growth: uneaten food breaks down and adds toxic waste to the aquarium.

FishBase records adults eating worms, crustaceans, insects and plant matter in nature. It also notes aquarium feeding on green algae and acceptance of dried food. Seriously Fish describes the species as an omnivore that consumes zoobenthos and detritus, and recommends a good proportion of vegetable matter.

Build the meal from supported foods

• Dried component: use a good-quality flake or granule with a high algae content.
• Vegetable component: include vegetable flake or blanched spinach.
• Animal-based variety: offer small live or frozen foods such as daphnia, small bloodworm or tubifex.

Rotate these foods rather than depending on one item. A dried product provides a practical routine meal, an algae-based food or prepared vegetable contributes the plant component, and small live or frozen foods reflect the animal material recorded in the diet.

Use appetite as a daily check

Watch the whole group during feeding. Confirm that each fish approaches food and that one individual is not consistently missing the meal. Reduced intake or a lack of interest in food is one of OATA’s health warning signs, especially when it appears alongside altered swimming, breathing, colour or body condition.

Adjust the portion from what you observe

Start with a modest amount and watch the fish for the full few-minute feeding period. If food remains after that period, reduce the next daily portion rather than allowing leftovers to accumulate in the substrate. If one fish repeatedly misses the meal while others feed, check its swimming, breathing, colour and body condition and test the water before changing the whole group’s ration.

Keep variety separate from quantity. Rotating dried food, vegetable matter and small live or frozen items broadens the diet, but it does not justify a larger daily meal. Feed only the amount the group consumes within a few minutes. This keeps the animal and vegetable components in the routine while limiting the uneaten material that would otherwise break down into aquarium waste.

Plan companionship without assuming the sex supplied

OATA suggests keeping at least three guppies or mollies together because these fish require companionship. Treat three as the starting group number, then check that the approximately 81-litre aquarium and 90 × 30 cm base can accommodate the complete adult community.

One purchase supplies one animal, so one purchase alone does not form the suggested group. Existing compatible mollies can contribute to the group plan, but they still count towards the aquarium’s total occupancy and filtration load.

Use a female-biased ratio when sexes are known

OATA suggests two females to each male, while Seriously Fish recommends several females for every male because males can pursue females persistently. Apply that ratio only where the sexes are known reliably; do not infer the sex of the fish offered here from its dispatch size, colour or gallery illustration.

Dense planting helps provide cover. It also gives fish space to move away from repeated attention within the group. Continue to observe swimming, feeding and hiding behaviour after introductions, since a change from an individual fish’s normal pattern can be an early warning of stress.

Allow for live young

Mollies are livebearers and mixed-sex groups can produce live young. Account for possible population growth before assembling the group. More fish require more aquarium volume and increase the demand on the biological filter, so do not let reproduction turn an adequately sized plan into an overcrowded one.

Count the group before selecting quantity

If two compatible mollies already live in the aquarium, adding one animal brings the count to three and reaches OATA’s suggested starting number, provided the water, adult stocking and sex plan also fit. If the aquarium has no mollies, one purchase leaves the count at one; plan the remaining animals and the complete adult capacity before proceeding.

Do not use the group number by itself as a stocking calculation. Three mollies still need the hard, alkaline water, mature filtration and aquarium footprint described above. Where the sexes are reliably known, arrange the suggested female-biased ratio. Where they are not known, do not assign a sex from appearance; observe the group and keep enough planting and capacity to respond to persistent pursuit.

Protect water quality with a fixed weekly routine

At least once every week, change 25% of the aquarium water. Use a siphon to remove solid waste from the substrate, and treat replacement tap water with conditioner to remove chlorine or chloramine before adding it to the aquarium.

Test ammonia and nitrite at least once per week and keep both at 0 mg/l. OATA advises keeping nitrate no more than 20 mg/l above the normal tap-water level. Test pH and hardness regularly as well, because clear water can still be too soft, too acidic or chemically unstable for this molly.

Clean the filter without killing its bacteria

Check the filter for blockages. If it needs cleaning, do not run it under the tap. Lightly rinse the media in aquarium water removed during the partial water change. This method reduces the number of beneficial bacteria lost while clearing accumulated debris.

Respond to changes in the fish

• Check for hanging at the surface, sitting on the bottom or erratic swimming.
• Look for darker or paler colour, unusual hiding or increased aggression.
• Compare gill movement with the fish’s normal breathing rate.
• Inspect for white spots, fluffy growths, damaged fins, missing scales, bumps or ulcerations.
• Watch for weight change or reduced interest in food.

If any of these changes appear, test the water first. Correct detectable ammonia or nitrite and check temperature, pH and hardness against the target ranges. Contact us for further guidance when a health change persists or the cause is unclear; do not begin a treatment that has not been matched to the problem.

Keep the weekly sequence consistent

1. Observe swimming, breathing, colour, fins, scales, body condition and feeding before disturbing the aquarium.
2. Test ammonia and nitrite and compare nitrate with the normal tap-water level.
3. Check temperature, pH and hardness against 21–28°C, pH 7.5–8.0 and 15–18 dGH.
4. Remove 25% of the water while siphoning solid waste from the substrate.
5. Use the removed aquarium water to rinse filter media lightly when cleaning is needed.
6. Condition the replacement tap water before adding it to the aquarium.

Recording each result makes changes easier to identify. A move from 16 dGH to 15 dGH remains within the target, while a continuing fall towards softer water calls for investigation before it leaves the range. Any detectable ammonia or nitrite requires action even when the fish looks normal, because both targets are 0 mg/l.

Follow the arrival procedure in the right order

Prepare the aquarium before the parcel arrives. Confirm 21–28°C, pH 7.5–8.0, 15–18 dGH, 0 mg/l ammonia and 0 mg/l nitrite, and make sure the mature filter is operating normally.

How the fish is packed

The fish is hand-bagged in pure oxygen and placed in an insulated poly box, with a heat pack when the weather calls for it. Someone must be present to receive the parcel because live fish cannot be left unattended.

What to do on receipt

1. Receive the parcel in person.
2. Before opening it, start filming the sealed parcel with the outer box visible.
3. Open and inspect the parcel 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.
5. Release the fish after the floating period.

Film every delivery from the sealed parcel onward. A continuous unboxing video and the order number are required for a Live Arrival Guarantee claim, and the fish must remain visible inside the sealed bag before release.

Check the fish after release

Observe swimming, breathing, posture and interest in food after introduction. Compare behaviour with the warning signs in the weekly-care section and test the aquarium immediately if the fish hangs at the surface, sits on the bottom, swims erratically or breathes at a noticeably different rate.

Read the current delivery and Live Arrival Guarantee policy before the delivery date so the receiving, filming and acclimatisation steps are clear.

Screen every tank mate for hard, alkaline water

Keep the Lyra Molly Black only with fish that tolerate the same water conditions. Seriously Fish describes Poecilia sphenops as peaceful but does not recommend it for a general community because many common community fish do not share its hard-water requirements.

Begin the assessment with 21–28°C, pH 7.5–8.0 and 15–18 dGH. A candidate that requires softer or more acidic conditions fails the screening even if its temperament appears peaceful. Do not compromise by holding both species at the edge of unsuitable ranges.

Suitable categories after screening

• Other Poecilia that tolerate the same conditions, except Poecilia latipinna.
• Some rainbowfish whose own care requirements overlap the aquarium.
• Hard-water-tolerant barbs.
• Hard-water-tolerant tetras.

These are conditional categories, not universal approvals. Check the exact species, adult group, aquarium footprint and water requirements before adding it. “Rainbowfish”, “barb” and “tetra” each cover animals with different needs.

Avoid incompatible plans

• Avoid fish that cannot tolerate hard, alkaline water.
• Avoid an unscreened general community assembled around soft or acidic conditions.
• Avoid keeping Poecilia sphenops with Poecilia latipinna; Seriously Fish recommends keeping only one of these species per aquarium because they interbreed readily.

If you are considering a species outside the named categories, ask us with the aquarium volume, adult stocking plan and measured temperature, pH and hardness. Compatibility depends on the complete aquarium rather than the common name alone.

Reject a candidate at the first failed test

Start with the candidate’s complete temperature, pH and hardness needs. A fish that fits 25°C but needs pH 6.5 and soft water is not suitable for this aquarium. A fish labelled peaceful is also not suitable when its water requirements fail, because temperament cannot correct a chemical mismatch.

Next compare the adult stocking plan with the approximately 81-litre volume and 90 × 30 cm base. Preserve room for the suggested molly group, planted cover and open swimming space. Finally, check the identity: Poecilia latipinna remains excluded even when its water needs fit. Only candidates that pass water, space, social and identity checks should proceed to gradual introduction and observation.

Apply the compatibility rule to the whole aquarium

A workable example is an aquarium around 81 litres with a 90 × 30 cm base, measured at 25°C, pH 7.8 and 16 dGH. Those readings fit the routine targets. A planned group of at least three mollies can then be assessed alongside peaceful fish from the named categories that share those same conditions.

A poor match is a mature aquarium at pH 6.8 and 8 dGH. Maturation and filtration do not correct the mismatch: the water is still softer and more acidic than the Lyra Molly Black plan, and Seriously Fish links such conditions with rapid weakening.

Another unsuitable plan is mixing this fish with Poecilia latipinna. Shared water preferences do not remove the interbreeding issue, so keep the two species in separate aquariums.

Check in a fixed order

1. Water: confirm that every species can live at 21–28°C, pH 7.5–8.0 and 15–18 dGH.
2. Space: count each fish at its adult size and retain the 90 × 30 cm working footprint.
3. Social plan: preserve the suggested molly group of at least three.
4. Temperament: choose peaceful companions and observe the aquarium after each gradual addition.
5. Identity: exclude Poecilia latipinna from the aquarium.

Add fish slowly so the filter bacteria can adjust to the increased waste. Test ammonia and nitrite after additions as part of the established weekly routine, and pause further stocking if either is detectable.

Compare two complete plans

The passing example still requires gradual stocking, mature filtration and observation after each addition. The failing example cannot be repaired merely by choosing peaceful fish, because its pH and hardness remain outside the molly’s routine targets. Correct the aquarium plan first, then reassess every proposed resident against the same sequence.

Answer common Lyra Molly Black questions

How big does the Lyra Molly Black get?

The Lyra Molly Black reaches 7.5 cm standard length according to FishBase. Plan its aquarium and stocking around that adult figure rather than the dispatch size.

What size aquarium does the Lyra Molly Black need?

Use an aquarium with a 90 × 30 cm base and approximately 81 litres for the Lyra Molly Black, following the species profile from Seriously Fish. Allow more volume when adding further groups.

How many Lyra Molly Black fish should I keep together?

OATA’s guppy-and-molly guidance suggests a group of at least three, with two females to each male where the sexes are known. One fish on its own does not meet that suggested group number.

Is the Lyra Molly Black suitable for beginners?

OATA describes guppies and mollies generally as easy to keep, but the Lyra Molly Black needs a mature filtered aquarium, hard alkaline water and consistent weekly maintenance.

What does the Lyra Molly Black eat?

Feed the Lyra Molly Black once daily with only what it can eat within a few minutes. Use quality dried and algae-based foods, vegetable flake or blanched spinach, plus small live or frozen daphnia, bloodworm or tubifex for variety.

What temperature, pH and hardness does it need?

Keep this fish at 21–28°C, pH 7.5–8.0 and 15–18 dGH, the overlap of FishBase’s recorded range, Seriously Fish’s species guidance and OATA’s guppy-and-molly guidance.

Is this fish aggressive or likely to nip fins?

Seriously Fish describes it as peaceful. Keep it with peaceful fish that tolerate the same hard, alkaline water, and observe behaviour after every gradual introduction.

Which kinds of fish can it live with?

Suitable candidates include other compatible Poecilia, some rainbowfish and hard-water-tolerant barbs and tetras. Screen each exact species for matching water needs, and avoid Poecilia latipinna because the two species interbreed readily.

How does it arrive alive?

Start filming the sealed parcel before opening or floating the bag, then record the continuous opening and the fish inside its sealed bag. It is packed in pure oxygen inside an insulated poly box, with a heat pack when needed; receive it in person, inspect it the same day and float the bag for 20–30 minutes before release.

Consult the care references

• FishBase: Poecilia sphenops — identity, distribution, recorded environment, diet and maximum length.
• Seriously Fish: Poecilia sphenops — species aquarium dimensions, water, feeding and compatibility.
• OATA: How to look after guppies and mollies — group care, feeding, maintenance and introduction guidance.
• RSPCA aquarium environment guidance — biological filtration and waste processing.