Molly

The Molly is a robust and adaptable livebearer fish that has become a cornerstone of the freshwater aquarium hobby. Available in various color varieties including black, gold, dalmatian, and lyretail, mollies are known for their hardiness and algae-eating tendencies. Native to coastal areas of Mexico and Central America, many wild populations are actually brackish water fish, which explains their tolerance for salt. They are larger than platies and guppies, with sailfin varieties displaying impressive dorsal fins. Mollies are excellent algae controllers, constantly grazing on tank surfaces and plants. They are peaceful community fish that work well in groups, though males can occasionally show mild aggression toward each other. Their tolerance for salt makes them unique among common community fish, and adding aquarium salt can actually improve their health and coloration. As prolific livebearers, they will readily breed in home aquariums.

Care Requirements

Tank Setup

Mollies appreciate a well-planted tank with open swimming areas. They grow larger than many community fish, so provide adequate space. Use hardy plants as they may nibble on soft vegetation. Include algae-covered rocks or driftwood for grazing. Filtration should be moderate to strong as they prefer well-oxygenated water. They benefit from the addition of aquarium salt (1-2 tablespoons per 5 gallons).

Water Quality

• Temperature: 75-82°F (24-28°C)
• pH: 7.5-8.5 (alkaline)
• Water Hardness: Hard (15-30 dGH)
• Ammonia/Nitrite: 0 ppm
• Nitrate: <40 ppm
• Salt: 1-2 tbsp per 5 gallons (optional but beneficial)

Regular water changes (25-30% weekly) are important to maintain water quality.

Feeding

Herbivorous-leaning omnivores. Feed:

• High-quality vegetable-based flake or pellet food as staple
• Algae wafers and spirulina flakes
• Blanched vegetables: zucchini, cucumber, spinach
• Frozen foods: daphnia, bloodworms as treats (not too much protein)

Feed 2-3 times daily. They constantly graze on algae and biofilm between meals.

Behavior & Compatibility

Peaceful and social fish that do best in groups of 4-6 or more. Males may show mild chasing and sparring but rarely cause harm. They are active swimmers that utilize all water levels. Excellent community fish compatible with most peaceful species. They help control algae by grazing on tank surfaces and plants. Maintain a ratio of 1-2 females per male.

Common Health Issues

1. Shimmies: Stress-induced condition causing shaking; caused by soft water, low pH, or stress. Add aquarium salt and improve conditions.
2. Fin rot: Usually from poor water quality
3. Ich: Treat with increased temperature and medication
4. Dropsy: From poor water conditions; maintain pristine water

Breeding

Livebearers that breed readily. Females can store sperm and produce multiple batches. Gestation lasts 4-6 weeks, producing 20-100+ fry per batch. Fry are born fairly large and can eat crushed flake immediately. Dense planting or a breeding trap improves fry survival. Fry grow quickly with proper feeding.

Tips for Success

• Add 1-2 tablespoons of aquarium salt per 5 gallons for optimal health
• Maintain alkaline water conditions (pH 7.5+)
• Keep in groups of 4+ fish
• Provide vegetable-heavy diet
• Ensure good filtration and water movement
• Watch for shimmies and add salt if symptoms appear
• Remove pregnant females only if using breeding traps