🧴Water care for a Molly: 24 to 28°C, pH 7.5 to 8.5
Molly : 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.
🩺 Reminder: this page informs, it does not diagnose. For any symptom or health question, your veterinarian remains the only reference.
In short: 6 to 10 cm as an adult, 100 L minimum for a group, hard water between 24 and 28 °C. Active, sociable and a keen grazer, it enlivens the surface and decor all day in a female-dominant group. It needs warm, hard, alkaline water: in soft acidic water it quickly develops the shimmying disease.
The Molly’s water: its real parameters
Temperature of 24 to 28°C, pH of 7.5 to 8.5, undetectable nitrites and nitrates under 25 mg/L: that is the contract. A drop-test kit (NO2, NO3, GH, KH, pH) beats any strip — and the nitrogen cycle, three to four weeks before any fish, is non-negotiable.
Water changes and tank upkeep
10 to 20% of the volume weekly, with water pre-heated to tank temperature: thermal shock stresses more than imperfect water, gentle substrate siphoning as you go and filter media rinsed in tank water, never under the tap: chlorine sterilises your filter.
Health: what stalks the Molly
In the Molly, watch for: shimmying disease in unsuitable water and white spot disease in weakened fish. But the golden rule holds for the whole tank — nearly all disease starts in degraded water or chronic stress, and you ALWAYS test the water before reaching for medicine. Well kept, a Molly lives 3 to 5 years.
Frequently asked questions
What water parameters for a Molly?
24 to 28°C, pH 7.5 to 8.5, zero nitrites and nitrates under 25 mg/L — checked with drop tests, not by eye.
How often should a Molly tank get water changes?
10 to 20% weekly, water brought to temperature, filter rinsed only in tank water. Consistency beats volume.
The guides that apply to you
- Gravel vacuum: cleaning the substrate without breaking the nitrogen cycle
Running a gravel vacuum removes waste built up in the substrate without destroying the filter's useful bacteria. The right frequency and technique for effective, risk-free cleaning.
- Power Outage: Why Goldfish Outlast Tropical Fish Without Aeration
A scientific discovery explains why goldfish survive longer than tropical fish during an aeration or filtration outage.
- Filamentous (Hair) Algae in Aquariums: Causes and How to Get Rid of It
Long green strands cling to plants and decor and grow back within days of every cleanup. Understanding why filamentous algae thrives before reaching for a lasting fix.
- High Nitrates in Your Aquarium: Where They Come From and How to Lower Them
Unlike nitrites, nitrates do not kill within hours, but a persistently high level stresses fish and weakens the tank. Where they come from and concrete ways to bring them down.