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.
An accessory from our shop for this use: Hang-on isolation and breeding box for aquariums (€28.90) · the whole shop
Outside our shipping area? The downloadable practical guide: Beginner axolotl: aquarium and care (€19)
🩺 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
- Old tank syndrome: why a sudden big water change can do harm
A long-neglected aquarium adapts to high nitrates. A sudden large water change can then shock the fish rather than help them. Understanding this risk and avoiding it.
- Should you change all the aquarium water? No, and here is why
Changing all the aquarium water destroys the bacterial balance and stresses the fish. Best practice: 10 to 25 % per week. Method and special cases.
- Damaged Fin: How Does a Fish Actually Regrow It?
A scientific review explains how a fish regenerates an injured fin and what speeds up or slows down that regrowth.
- Buying the fish and the aquarium on the same day: why it is the fatal mistake
Buying fish and aquarium the same day exposes your fish to the ammonia spike: 3 to 4 weeks of cycling are essential. Explanations and timeline.