Yes, they can. First of all, mollies and guppies are incredibly similar.
Secondly, both species are easy to care for, so much so that many newcomers choose mollies and guppies as their first fish.
Can they become violent? Yes, they can, but only if you expose them to the wrong conditions. Otherwise, they will get along splendidly.
Can I Keep Molly Fish And Guppies In The Same Tank?
Guppies and mollies are frequently confused for each other by newcomers because they share so many attributes.
This works in your favor because they can occupy the same aquatic space. You have room to experiment since both creatures are hardy.
They can tolerate conditions that don’t fit within their preferred parameters, at least for a little while. Although the wrong parameters will incite violence in mollies and guppies.
They are more likely to fight one another if you keep them in small, crowded tanks with cold water and the wrong pH and hardness.
Also Read: 19 Great Molly Fish Tank Mates
Mollies vs. Guppies: Behavior
The temperament is somewhat tricky because fish have distinct personalities.
You can find aggressive fish in peaceful species and peaceful fish in aggressive species. This is why fish size matters.
Aggressive fish are less likely to destroy your tank if their peaceful neighbors are larger and strong enough to defend themselves.
In this case, mollies and guppies are similar in size. Mollies are usually bigger. But they are not large enough to bully the guppies.
If they ever fought, the guppies would hold their own. Therefore, natural behavior will determine whether these creatures can co-exist.
Also Read: Guppy Fish Tank Mates
Molly Fish: Natural Behavior
Mollies are peaceful, sociable fish that prefer to live in groups of four or more. A large group prevents unnecessary conflicts because it gives mollies a sense of security.
As such, they are less likely to respond violently to crowded conditions, extreme temperatures, and aggressive neighbors.
Nonetheless, you should encourage the mollies to behave by raising them in a clean, well-maintained tank with the appropriate conditions.
Guppies: Natural Behavior
Guppies give what they get. They respond violently to aggressive fish.
On the other hand, they will behave if you pair them with peaceful neighbors. Some aquarists avoid them because of their energetic personalities.
They can antagonize slow-moving neighbors, especially when they develop fin-nipping habits.
But mollies are the same. Molly fish and guppies are too similar to harass one another. But again, fish have distinct personalities.
Don’t be surprised if a random guppy or molly fish decides to lash out without provocation.
If the aggressive fish is new, you probably forgot to acclimate it before adding the creature to the aquarium.
Also Read: Guppies Chasing Platy And Molly Fish
Ideal Parameters For Molly Fish And Guppies
| Parameters | Temperature | pH | Hardness |
| Guppies | 72 to 82 (F) | 6.8 to 7.8 | 8 to 12 dGH |
| Molly Fish | 72 to 78 (F) | 7.5 to 8.5 | 15 to 30 dGH |
Molly Fish: Ideal Parameters
Mollies are relatively ordinary freshwater fish from tropical regions with conventional requirements.
Their temperature (72 – 78) and pH range (7.5 – 8.5) are easy to maintain.
You can raise the water by several degrees without harming the mollies. They are hardy enough to tolerate poor conditions without developing irreversible illnesses.
Guppies: Ideal Parameters
Like the mollies, guppies live in warm waters in the wild. They are hardy enough to live in cool conditions. But their rate of growth will slow. They will also breed less frequently.
Their temperature range is wider than people think, which gives you some breathing room. But you should keep the temperature in the 70s for the best results.
Also Read: Can Neon Tetras And Guppies Live Together?
Molly Fish And Guppies: Ideal Conditions
| Requirements | Guppies | Molly Fish |
| Ammonia | 0ppm | 0ppm |
| Nitrite | 0ppm | 0ppm |
| Nitrate | Less than 20ppm | Less than 20ppm |
| Tank Size | Minimum 20 gallons | Minimum 20 gallons |
| Foliage | Yes | Yes |
| Decorations | Yes | Yes |
| Filter | Yes | Yes |
| Heater | Yes | Yes |
| Salt | Sometimes | Sometimes |
Molly Fish: Ideal Water Conditions
If your mollies keep dying, don’t fret. You’re not alone. Newcomers forget that mollies are not strictly freshwater fish.
You will find them in freshwater, brackish water, and saltwater. If a breeder lives in a location where saltwater is cheaper than freshwater, they will raise their mollies in brackish water.
If you buy those fish from a local retailer and transfer them to a freshwater aquarium, they may die because of the damage their kidneys have sustained.
This doesn’t mean your molly fish tank needs salt. Talk to the retailer. They can advise you accordingly because they know the molly’s origins.
Many experts recommend hard water because soft water attracts illnesses such as ich. Mollies sound complex, but they are incredibly adaptable.
Unless you find a unique type that can’t tolerate conventional conditions in a freshwater aquarium, anyone can raise mollies regardless of their expertise.
Guppies: Ideal Water Conditions
Any tank that accommodates mollies can support guppies.
They want hard water with adequate minerals and a heater to maintain a stable temperature. The hotter the water, the faster the fish will grow.
Give them plants and decorations to combat stress. Avoid decorations with sharp edges. The lighting doesn’t matter.
So long as you maintain a regular day/night cycle and avoid excessively bright lights, the guppies will thrive.
Talk to a vet or your local retailer before you add salt. Some people use it to great effect. But in other cases, it does more harm than good.
The Dietary Requirements Of Molly Fish And Guppies
| Food | Guppy Fish | Molly Fish | Quantity | Schedule |
| Fish Pellets and Flakes | Yes | Yes | Small Pinch | 7 Days |
| Tubifex Worms | Yes | Yes | Small Pinch or Less | 2-3 Times Weekly |
| Bloodworms | Yes | Yes | Small Pinch or Less | 2-3 Times Weekly |
| Brine Shrimp | Yes | Yes | Small Pinch | 1 – 2 Times Weekly |
| Vegetables | Yes | Yes | Small Pinch | Twice Daily |
| Daphnia | Yes | Yes | Small Pinch | 1 – 2 Times Weekly |
| Mysis Shrimp | Yes | Yes | Small Pinch | 1 – 2 Times Weekly |
| Maggots | Yes | Yes | Fish can eat their weight in maggots | 2- 3 Times Weekly |
| Algae | Yes | Yes | No Limit | They can eat the algae in the tank whenever they want. |
Molly Fish: Ideal Dietary Requirements
As omnivores, mollies are not picky. They will eat whatever you add to the tank, from lettuce and zucchini to bloodworms, brine shrimp, flakes, etc.
While live and organic foods are preferable, you can raise them on high-quality flakes and pellets.
Because they eat algae, they can survive without food for a while. But you can’t trust them to keep your algae population under control.
Guppies: Ideal Dietary Requirements
Like mollies, guppies are algae eaters. But you can’t rely on a tank’s natural algae population to satisfy them.
They need algae wafers, flakes, pellets, and live, frozen, and freeze-dried foods. Give them a mixture of animal and plant matter to keep the guppies healthy and disease-free.
They should eat once or twice a week in quantities they will finish within the first two to five minutes. The more food you give them, the more leftovers you get.
Also Read: Can Angelfish And Guppies Live Together?
Ideal Tank Size For Keeping Molly Fish And Guppies Together
Both species breed easily. But you need at least two females for every male fish to maintain peace.
Twenty gallons should be the starting point. Larger molly fish types may require 55 gallons or more.
Also Read: Can Guppies And Mollies Crossbreed?
Best Tankmates For Molly Fish And Guppies
If you’re looking to add variety to your aquarium, having only mollies and guppy fish can become monotonous.
Nevertheless, if your tank has a capacity of 20 gallons or more, there are other options to consider.
Here are a few peaceful species that can live together harmoniously in your tank:
- Cory Catfish
- Platys
- Gouramis
- Swordtails
- Harlequin Rasboras
- Cherry Barbs
- Zebra Loaches
- Neon Tetras
Also Read: Mollies And Neon Tetras
Fish To Avoid With Mollies And Guppies
However, it is advisable to steer clear of introducing aggressive species. I strongly discourage adding:
- Angelfish
- Oscars
- Tiger barbs
- African cichlids
- Red-tailed sharks
- Siamese fighting fish (Betta fish)
- Jack Dempseys
Conclusions
If you are in a rush, here is a brief summary of what I talked about earlier:
- Mollies and guppies can live together peacefully as they share many similarities.
- The compatibility between mollies and guppies depends on maintaining the right conditions and avoiding aggression-inducing factors.
- Both mollies and guppies have specific ideal water parameters and dietary requirements that should be met for their well-being.
- The tank size should be a minimum of 20 gallons to accommodate mollies and guppies together, with larger tanks recommended for certain molly fish types.
- When seeking tankmates, peaceful species like Cory Catfish, Platys, Tetras, Harlequin Rasboras, and Zebra Loaches can coexist harmoniously, while aggressive species like Angelfish, Oscars, Tiger barbs, African cichlids, Red-tailed sharks, and Jack Dempseys should be avoided.