How to Care for Mollies

Keep your mollies in a 20-gallon or larger aquarium. If your mollies are some of the larger hybrids, like balloon mollies, start with a 30-gallon tank. Avoid overcrowding mollies in an aquarium that is too small, which can lead to water quality problems and several types of diseases. Mollies have the ability to thrive in either saltwater or freshwater tanks. For freshwater aquariums, add one teaspoon of aquarium salt per gallon to keep them healthier. Mollies prefer a water pH of 7 to 7.8. Use a filtration system suitable for the size of the aquarium.

Provide plenty of vegetation for the mollies, which enjoy having places to hide, especially if they are giving birth. Use either live or plastic plants. Live plants that mollies like are Anubias, Sagittaria and Vallisneria. They will nibble on the live plants as well for nourishment. Add aquarium decorations and figurines for visual interest to aquarium landscapes and to provide hiding places for your fish.

Feed mollies plant-based food flakes. Mollies can also eat dried or frozen bloodworms, brine shrimp or tubifex. Ensure the basis of their diet is plant- or algae-based food. Feed mollies once a day and no more than they can eat in five minutes. Overfeeding leads to more waste in the tank. Thaw frozen food first.

Change the water in the tank regularly. Remove 10 to 25 percent of the water from the tank once every two to four weeks and replace it with clean water. Treat the clean water first with a chlorine remover so it is safe for the mollies. Water changes keep waste and nitrate levels down to prevent disease and illness. Use kits available at most pet stores to test the water quality every week.

Keep the tank water 68 to 82 degrees Fahrenheit. Any hotter or colder will be stressful for the mollies. Several types of water heaters are available to place in fish aquariums. Monitor water temperatures with a thermometer kept inside the tank. When changing water in the tank, make sure the new water is close in temperature to the remaining water in the tank.

Place other mild-natured fish species with your mollies. Suitable fish to house with mollies include plecos, loaches, barbs, tetras, danios, rasboras, platies, guppies and scavenger catfish. Do not overcrowd the tank. A general rule of thumb is for every inch of fish, there should be one gallon of water.

Provide the proper habitat for mollies if you plan to breed them. Mollies are live-bearing fish, which means they give birth to live young instead of laying eggs. Healthy mollies will breed often and produce many young. In breeding tanks, include planted vegetation or a thick algae mat for the young to hide in. Mollies will produce 10 to 60 young every 60 to 70 days. The young mollies will be about 1/2 inch long. If the fish in the tank are underfed, the adults will eat the young. Partition the tank with a plastic aquarium divider, if desired, to separate the adults from the young.