Mollies Care Guide

Molly (Poecilia latipinna/Poecilia sphenops) is a small size tropical fish that originates from South and Central America. Mollies are typically found in freshwater streams, but they are also known to inhabit brackish coastal seawaters or swamps.

They have a quite unique ability to be able to live in both freshwater and salt water. This ability, coupled with their peaceful nature and colorful body, is what makes them one of the most popular species among fish-keepers worldwide.

Black Molly


Different Types

There are a lot of different types of mollies available; as with every other fish species, mollies are hybridized in search for the better, more colorful, interesting specimen.

However, there are two species that are most common in the aquarium world: sailfin mollies (poecilia latipinna) and short-finned mollies (poecilia sphenops). Almost all other types originate from one of these two most common types.

Both of these diverse species are fairly simple to keep, but if you really want them to thrive, you should learn and master all the particulars associated with each. Here are some tips that might help you along the way.

Tank size suitable for mollies

The tank size suitable for keeping this fish depends on a few different factors with the most important being the particular fish species you want to keep.

Short-finned molly needs a ten-gallon aquarium, but if you really want your fish to thrive, you should consider a longer twenty-gallon aquarium.

If you opt for the larger sailfin molly, you should consider at least a twenty-gallon aquarium for their housing. Another important factor is bigger aquariums are more stable in terms of water quality fluctuations.

This is significant for mollies because they are very susceptible to sudden changes in water parameters.

Water quality

Mollies are known for their adaptability and hardiness; however, you should strive for an optimal environment for their keeping. The easiest way to do this is to simply simulate their natural environment by using an ideal water temperature anywhere between 70-85⁰ Fahrenheit.

It is highly recommended to keep water temperature as stable as possible to avoid unneeded stress for your fish.

This fish also prefer hard water (15-30 dGH) and thrive at a higher water pH, preferably 8.0. The ideal pH varies for different types of mollies, but the values from 7.5 to 8.5 are always satisfactory.

It is known mollies thrive in heavily filtrated water, although they are quite capable of adapting to different environments.  Experienced aquarists recommend higher than average water filtering for mollies.

Even though mollies aren’t untidy, the general recommendation is to change at least one third of the water on a weekly basis; make sure to change the water steadily in order to keep the changing process less stressful for your fish.

Type of water suitable for molly

Although mollies are predominantly fresh water species, they are known to live in brackish and even salty waters. This creates a debate among aquarists on whether you should add salt to your tank or not when keeping mollies.

The answer is anything but simple and it depends on the particular species that’s being kept. In general, there’s nothing pointing to the fact adding salt in fresh water is needed whatsoever.

Most mollies will thrive in completely freshwater tanks with no extra salt needed. With this in mind, it’s generally just a personal preference whether or not the salt should be added.

Feeding your mollies

Mollies are considered omnivores. You should generally feed them a varied diet with high-quality flake food and many vegetables because they consume algae and plants in their natural habitat.

Frozen food is also great for mollies though, as far as live food, they prefer daphnia, brine shrimp, and bloodworms.

The best way of feeding mollies is two or three times a day on average. As with every other fish species, be aware of overfeeding, especially given the fact mollies are known to eat more than they need to.

Only feed as much food as they can eat in three to five minutes. This practice will help your fish stay healthy and will greatly improve your water parameters as well.

Breeding your Molly

Mollies are live bearers, quite unlike many other species of tropical freshwater fish, meaning they give birth to live young instead of laying eggs. The best male to female ratio is one male molly per three or four females.

This is because males are notorious for chasing females and consequently stressing them with mating attempts. Having more females helps reduce stress by spreading the tension between multiple females.

Molly fish prefer warmer water when breeding thus 80-82⁰ Fahrenheit is the best water temperature. Being heavy breeders, female mollies can give birth to anywhere from 5 fries to 100 or even more.

The best practice is to keep the fry in a separate aquarium up until they reach the size where they cannot be molested or eaten by other fish. When very young, feed them five times a day or more with powdered flakes or baby brine shrimp.

Live plants and algae also do wonders in keeping their diet diverse.

Suitable Tank Mates

Mollies are considered to be peaceful fish. They live in groups and many have had success with keeping them in community aquariums. However, others prefer to keep them in a single species aquarium because they can become aggressive toward other fish as well as between each other.

They are known to nip the fins of other fish occasionally and males are very aggressive when kept alone without females to keep their attention.

The opinions are split on this one and the best piece of advice is to practice if your mollies are good to keep in a community aquarium.

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