Molly: gear and buying guides
The molly is an active, sociable livebearer that reaches 6 to 10 cm and needs more room than a guppy: 100 L minimum. It requires warm water at 24 to 28 °C, hard and alkaline, with some strains even tolerating slight salinity. A keen algae grazer, it enlivens the surface and decor all day long.
Profile : 6 to 10 cm as an adult, 100 L minimum for a group, hard water between 24 and 28 °C.
See it in the Planète Pets shop: Resin shipwreck hide for aquariums, 4 models (€26.90) · the whole shop
We don’t ship products to your country yet; our practical guide downloads anywhere: Beginner axolotl: aquarium and care (€19)
Species profile
- Lifespan
- 3 to 5 years
- Adult size
- 10 cm
- Minimum tank
- 100 L
- Water temperature
- 24 to 28 °C
- pH
- 7.5 to 8.5
- Temperament
- Active, sociable and a keen grazer, it enlivens the surface and decor all day in a female-dominant group.
- Health watch
- shimmying disease in unsuitable water · white spot disease in weakened fish
🩺 This health information is general in nature and does not replace a consultation: at the slightest doubt about your animal’s condition, talk to your vet.
Molly gear, family by family
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Food
Strongly vegetarian: spirulina and blanched vegetables should dominate, supplemented with flakes and occasional frozen foods. A lack of plant matter weakens its digestive system.
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Care & grooming
Delicate in soft acidic water, where it readily develops the shimmying disease. Keep the water hard, alkaline and warm, with a 25 percent weekly water change.
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Toys & enrichment
Sturdy plants that tolerate hard water, calcareous rocks and algae-covered grazing surfaces. It enjoys gentle surface agitation and areas with some current.
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Bedding & habitat
A tank of at least 100 L, fairly tall and long, for a group with a majority of females. A prolific species: plan ahead for the many fry.
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Travel & safety
Warm bag transport is essential, as it copes poorly with temperature drops. Gradual acclimation of 30 to 45 minutes, especially if water hardness differs.
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Accessories
A 100 to 150 W heater, generous filtration, GH/KH tests and possibly mineral salts to reharden the water. Budget around 120 to 200 euros for a 100 to 150 L tank.
🎾 Enriching a Molly tank: hardscape, shoal and occupation
Hardscape designed for its swimming zone
The swimming zone dictates the decor: a Molly moves in midwater, so tall plants at the back, wood as refuge and genuine swimming lanes organise its volume. An aquarium’s enrichment is its hiding places and its currents — not fluorescent ornaments.
Group life: the first enrichment
Read the Molly’s behaviour in its numbers: at 5+ you get displays, hierarchies and group swimming; below, a dull, stressed fish that hides — group size is the species’ first “toy”, before any decor purchase.
Food as occupation
Every Molly meal can become a hunt: release prey into the filter flow and move the feeding point from day to day — occupation comes from searching, not abundance.
Quick answers
- How many Molly should be kept together?
- 5 minimum, more if the tank allows: it is a group species, and numbers shape its behaviour and colours alike.
- How do you enrich a Molly tank?
- Through layout above all: decor designed for its living zone (in midwater), meals served in varied ways and a complete group — gadgets add nothing.
See it in the Planète Pets shop: Tall artificial aquarium plant, 45 to 49 cm, weighted base (€23.90) · the whole shop
We don’t ship products to your country yet; our practical guide downloads anywhere: Beginner axolotl: aquarium and care (€19)
🏠 The Molly tank: 100 L, hardware and start-up
100 litres minimum: why that number
For a group of 5+ Molly reaching 10 cm as an adult, plan 100 real litres — and remember a big tank is more STABLE, hence easier, than a small one: parameters drift slowly, leaving time to correct. This volume suits a sturdy standard cabinet — just verify perfect levelness.
Hardware: filter, heater, lighting
The Molly tank’s technical trio starts with filtration — three to five volume turnovers per hour, a heater around 1 W per litre set to 24 to 28°C, backed by an independent thermometer — built-in thermostats sometimes lie, and lighting on a timer at 8 to 10 hours a day: any longer and the algae win.
Substrate, plants and start-up
Nutrient substrate under fine sand or quartz, robust plants (anubias, vallisneria, Java moss) and wood to structure the territory. Then patience: a complete nitrogen cycle (3 to 4 weeks, nitrites back to zero) before the first Molly — the step every hurried beginner pays for dearly.
Quick answers
- What tank size for Mollys?
- A real 100 litres minimum for a group of 5+ — below that, parameters drift too fast to catch.
- Does a Molly need a heater?
- Yes, about 1 W per litre set to 24 to 28°C, with an independent thermometer double-checking the thermostat.
In our shop, for this use: Hollow moss-effect resin log for aquariums (€20.90) · the whole shop
Outside our shipping area? The downloadable practical guide: Beginner axolotl: aquarium and care (€19)
🧰 Accessories for a Molly: tests, upkeep and budget
Water tests: your dashboard
A drop-test kit (€15-30) is THE first accessory for a Molly tank: NO2 and NO3 weekly, GH-KH-pH at any doubt. Add a net sized to a 10 cm fish, a gravel siphon for water changes and a bucket reserved for the aquarium — detergent traces in a household bucket can poison a tank outright.
The Molly specifics
a battery backup air pump: at full stocking, a filtration failure is measured in hours.
The full budget, no surprises
An equipped 100 L setup (tank, filter, heater, lighting, substrate, decor, tests): expect €200 to 450 upfront, then €10 to 25 a month (food, electricity, conditioner). Second-hand often halves the tank price — only the filter and heater deserve to be new. Details on the full Molly profile.
Quick answers
- Which accessories are essential for a Molly tank?
- Drop tests, siphon, net, dedicated bucket, an independent thermometer: the whole kit stays under €60.
- What budget for keeping a Molly?
- €200 to 450 to set up an equipped 100 L tank, then €10 to 25 a month in routine costs.
An accessory from our shop for this use: Mini USB aquarium air pump with tubing and air stone (€22.90) · the whole shop
Outside our shipping area? The downloadable practical guide: Beginner axolotl: aquarium and care (€19)
Guides to read
- Community aquarium or species-only tank: which is right for a first setup?Bedding & habitat
Community aquarium or species-only tank: pros, cohabitation risks and advice for choosing how to set up your first aquarium.
- Best easy aquarium plants without CO2 for beginnersToys & enrichment
Which aquarium plants can you choose without CO2 injection? A selection of hardy, easy plants for a beginner's planted tank.
- Budget for a first brackish water aquarium: the real cost to get startedBedding & habitat
How much does a first brackish water aquarium cost? Tank, filtration, salt and salinity monitoring, budgeted item by item.
- Changing filter media too often: the mistake that wrecks your aquarium's cycleCare & grooming
Why you should never replace all your filter media at once: nitrifying bacteria, replacement frequency and the right habits.
- Restarting a neglected aquarium: a step-by-step guideCare & grooming
How do you restart an aquarium that's been left neglected without endangering the fish? Steps, water changes and mistakes to avoid.
- GH, KH and pH: understanding and adjusting aquarium water hardnessCare & grooming
GH, KH, pH: what do these three readings actually measure, and how do you adjust aquarium water hardness without stressing the fish?
- Upgrading to a bigger aquarium: moving your fish without the stressBedding & habitat
How do you upgrade to a bigger aquarium without breaking the biological cycle or stressing your fish? Steps and mistakes to avoid.
- Aquarium electrical safety: GFCI protection and good habitsTravel & safety
Heater, filter, lighting near the water: what electrical precautions keep an aquarium safe for fish and people?