Molly Fish and Guppy Fish – Can You Keep Them Together?

If you want to set up an aquarium with multiple types of fish, a good starting point would be to choose fish that are similar in nature and have the same water and feeding requirements.

This will ensure an environment in which your fish can feel comfortable and won’t be exposed to injuries or stress.

If you’re hoping to keep guppies and mollies in the same aquarium, and you’re wondering if guppy fish and molly fish can be kept together, you’re in luck!


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Molly fish and guppy fish are compatible and can be kept in the same aquarium. They’re both peaceful fish, they’re livebearers and they have very similar keeping and feeding requirements.

In what follows, you’ll find a short description on the requirements of mollies and guppies and my tips on how to keep these two fish together.

Guppy Fish

Guppies are not just beautiful fish that can add color to your aquarium, they’re also very useful. In the wild guppy fish feed on mosquito larvae, which makes them an excellent predator of disease-carrying mosquitoes, keeping their population under control.

In home aquariums, guppy fish average at around 2 inches, yet they require ample swimming space being active fish that like to explore their environment.

A 10-gallon tank is the very minimum that you should set up for them, however, a bigger tank will certainly not be lost on them.

When stocking your aquarium with guppies, do make sure that they’re more females than males. In fact, limit the number of males as much as possible.

As livebearers, guppies will breed constantly and populations can get out of control, therefore, add no more than 1 male for three females.

Keep the temperature in the aquarium somewhere between 72–79°F and bear in mind that they enjoy a bit harder water and a pH in the 6.8 – 7.8 range.

Come feeding time, be careful not to get tricked by your guppies into feeding them more food that they should eat. They’re voracious eaters and they’ll eat as much as offered, but you should be careful not to overfeed.

They’ll accept most types of fish food, but you should make sure they have enough variety and their diet includes meaty and vegetable foods.

Molly Fish

Mollies are larger than guppy fish, averaging somewhere around 4 inches, which means they’ll need a bigger tank.

Therefore, a 20-gallon aquarium is a good starter size, however, if you can do bigger, I encourage you to do so as mollies require a planted tank (plants take up space) and they’re active fish too.

Just like guppies, mollies are also live-bearing fish that can breed out of control, therefore, the same advice I mentioned when discussing guppies, applies for mollies too — limit the number of males in the aquarium to keep them from breeding too much.

As for water requirements, the ideal range for mollies is around 75-82° F, with pH at 6.7 and 8.7. Some molly fish varieties enjoy brackish waters, but most mollies are absolutely fine with freshwater.

Molly fish require an aquarium heater to keep water temperature stable, especially if you live in a non-tropical climate.

Mollies not only breed a lot, but they also swim a lot and eat a lot, which means their waste production is high. You should also invest in a filter system to help keep their water clean.

In terms of food, mollies are omnivores and they’ll accept a variety of foods from flakes to frozen and live foods.

How to Keep Mollies and Guppies Together

Here are some tips that can help optimize your aquarium in a way that will benefit both guppies and mollies:

1.  Choose a larger aquarium

Yes, you may get away with a smaller aquarium when keeping guppies, but a small tank won’t do if you’re keeping mollies too.

Aim to set up a 25 gallon or bigger tank and add live plants that can serve as hiding space for adult fish and fry.

2.  Limit the number of males

If there are males in the tank, you better believe there will be fry too. Unfortunately, if juveniles ate not separated from adults, you may not be able to enjoy their presence for too long as both mollies and guppies are known to eat their own fry.

Having lots of hiding places including densely packed plants can also help. Alternatively, you can set up a breeding box too to help save the fry from the adults.

Mollies and guppies can even breed amongst themselves too, so population control can be very difficult. Plus, female fish can already be pregnant when you buy them from the store, so I would argue it’s best to keep only males from both fish species.

3.  Add plants, heater, and filter system

Plants will not only serve as a hiding space for fry, but they will also help oxygenate the water and keep the water clean. Adding an aquarium filter will also help with water cleanliness.

Mollies enjoy warmer water and don’t do well with sudden temperature changes, therefore, adding a heater to your aquarium is a must.

4.  Be careful at feeding time – High-appetite fish can be tricky!

Mollies and guppies will always appear hungry because they have a high appetite. Unfortunately, feeding them too much food isn’t good for them or for the quality of their water.

Too much food leads to too much waste, which in turn causes the water to foul. Excess food can also adversely affect the health of your fish causing constipation or other digestive issues.

Therefore, make sure you feed your fish once or twice a day with an amount that they can eat in a few minutes.

Molly fish and guppy fish enjoy the same kinds of foods and they like to nibble on soft algae that grows on plants, so make sure their food is high in vegetable matter too!


Molly fish are a great companion for guppies, and you shouldn’t have any issues with keeping them together. Simply make sure to meet their water requirements, be careful with population control, and avoid overfeeding them.

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