Molly, Platy, Swordtail or Guppy – Which Fish to Choose as Beginner?

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Are you a new aquarist trying to build a beautiful tank? Then, you’re probably looking for the most important part of your aquarium display— the fish. With hundreds of species to choose from, the task might seem intimidating. But it doesn’t have to be!

In this article, I will help you narrow your list to only the most appropriate options. I’ve compiled all the information you need on four of the most popular and beginner-friendly species. Keep reading to discover the perfect aquatic pet for you!

Choosing Fish for Beginners

If you’re new to fishkeeping, you’ll obviously want to start with beginner-friendly fish species. But what makes a species suitable for beginners? This entails a few things, such as price, tank size, care requirements, and hardiness.

The best fish will come at an accessible price and have low setup and care requirements. That way, you don’t have to invest too much upfront. Mollies, Platies, Swordtails, and Guppies fit all these requirements quite nicely.

All four species have low space requirements. They’re all omnivorous and hardy, so they don’t need a special diet or care regimen. You won’t need a complex setup because neither of the species needs lots of light or fast-flowing water. But let’s see how they all compare.

– Molly Fish

Adult Size: Mollies are small to medium-sized. On average, adults measure 3.5–4.5 inches. Females are slightly larger than males and have rounder bellies. Molly fish take 4-6 months to fully develop and reach adult size.

Tank Space: Mollies are calm and friendly. Because they’re shoaling fish, they must live with other members of their species. You’ll have to keep at least four Mollies in the tank. You should provide at least 10 gallons worth of tank space for a small group of four, plus an additional 3 gallons for each extra Molly.

Water Parameters: The ideal water values include 72–78°F temperature, 6.7–8.5 pH acidity, and 15–30 dGH. As you can see, Mollies are pretty hardy. They can tolerate slightly acidic to alkaline water and hard to very hard water.

Tank Setup and Maintenance: For equipment, you’ll need a filter, a heater, and an airstone. Decorations include live plants, caves, and driftwood. Mollies are mid to top swimmers. They won’t be spending much time at the bottom of the tank, so the substrate is not that important.

Mollies are small but have a high bioload (they produce a lot of waste). To maintain stable water quality, you’ll have to perform weekly water changes, replacing around 25% of the water. You should also siphon the substrate each time you complete a water change.

Feeding: Mollies require feeding once or twice per day. Their diet should consist primarily of algae in the form of fresh algae or algae wafers. They’ll also eat green vegetables like spinach and lettuce. Mollies also need protein-rich foods on occasion. These include fish flakes and live or frozen brine shrimp and bloodworms.

Health: Mollies are a hardy species. They aren’t naturally predisposed to any illnesses. However, tank contamination or unsanitary conditions can cause ich, dropsy, velvet, flukes, or fin and tail rot. If caught early, these are easily treatable with medication.

Breeding: Mollies breed easily and are quite prolific. One female Molly can give birth to up to 100 fry, and the gestation period is as short as 50 days. If you don’t plan to breed your fish, you should keep males and females separate.

– Platy Fish

Adult Size: Platies are on the smaller side. Males reach up to 2 inches on average, while females measure up to 3 inches. Females also appear stouter than males. It takes 6-8 weeks for juveniles to reach their full adult size.

Tank Space: Unlike other livebearers, Platies aren’t a schooling species. You don’t have to keep them with other Platies if you need to save some space in the tank. However, they are still happiest living in groups of at least five. Each Platy requires at least 2 gallons of space. That makes up a total of 10 gallons for a small group.

Water Parameters: Platies require values between 70–77°F, 6.8–8.0 pH, and 10–28 dGH. In other words, they prefer slightly warmer temperatures, slightly acidic to alkaline pH, and moderately hard to very hard water.

Tank Setup and Maintenance: Platies are quick swimmers. They need lots of open space and hiding spots. Include lots of background and short plants, rocks, caves, and other decorations. Platies aren’t bottom-dwellers, so the substrate choice is up to you.

You’ll have to include a filter with a smooth flow, as Platies prefer slow-moving waters. Include gentle aquarium lights, as Platies need moderate light exposure. Remember to keep the aquarium lid on, as Platies are known jumpers!

Platies don’t produce much waste, but they still require at least a 25% water change once a week.

Feeding: Platies are voracious omnivores. They need a variety of foods, including fish flakes, algae pellets, live or freeze-dried foods (bloodworms, brine shrimp, daphnia, tubifex), and even some veggies (lettuce, zucchini, spinach, cucumber, squash).

Adult Platies should feed once or twice a day. A high-quality fish-flake feed should make up the majority of their diet. You can supplement this food source with algae pellets, veggies, and small invertebrates (in that order).

Health: Like Mollies, Platies are hardy and unlikely to develop diseases. The major ones to worry about are caused by infections due to unsanitary conditions or accidental tank contamination.

These include ich, velvet, fin and tail rot, or parasites. Always keep on top of the water changes and quarantine any new fish or plants before introducing them into the main tank.

Breeding: You won’t have to ask your Platies twice to breed. Even in the wild, this species is known for being prolific. As long as the conditions in the tank are ideal, a female Platy can give birth to up to 80 fry every 24-35 days.

– Swordtail Fish

Adult Size: Swordtails distinguish themselves from other livebearers due to their considerable size. The average Swordtail adult measures between 5.5-6.3 inches. As with other species, males are on the smaller side, while females are larger. It takes roughly six months for juveniles to develop into adults.

Tank Space: You’ll need 15 gallons for one Swordtail and an extra 5 gallons for each additional fish beyond that. Swordtails aren’t the best option if you have a small tank. Luckily, they aren’t a schooling species. They feel most comfortable in groups of at least 5, but you can keep less if you want.

Water Parameters: Ideal values include 64–82°F, 7.0–8.4 pH, and 12–30 dGH. Unlike other livebearers, Swordtails can tolerate cool and warm water equally well. They also prefer hard to very hard water. The pH should be at least neutral, but these fish prefer alkaline water.

Tank Setup and Maintenance: You’ll need a wide tank to provide lots of open space. Swordtails are energetic and active swimmers. The tank should also be heavily planted and provide plenty of hiding spots like caves and rocks.

A filter with a moderate flow is perfect. Swordtails become agitated in fast-flowing waters but still prefer some movement. Since these fish aren’t bottom swimmers, it doesn’t matter what substrate you choose. But they swim in the middle and top of the water column and aren’t strangers to jumping. So, make sure you invest in a stable aquarium lid.

Swordtails produce a lot of waste. You’ll have to monitor the water parameters and perform weekly water changes of 25-30%. Siphoning the substrate and wiping decorations and aquarium walls every two weeks also helps keep the aquarium clean.

Feeding: Swordtails are omnivores and prefer a protein-rich diet. The staple food for them should be quality flakes. These contain the right amount of protein, fat, carbohydrates, and minerals that the fish need.

Swordtails must also consume the occasional algae wafer or fibrous vegetables like spinach and peas. They need fiber in their diet for proper digestion. Live or freeze-dried invertebrates like bloodworms or brine shrimp should only constitute an occasional treat due to the risk of constipation.

Swordtails are larger than other livebearers, so it’s no surprise they also eat more. They require feeding two to three times per day. This is one major reason why they produce so much waste.

Health: Swordtail fish are hardy and unlikely to suffer from diseases. Again, they might develop infectious diseases like ich, fin rot, velvet, or cottonmouth. But these can affect any fish species if there is a bacterial, fungal, or parasitic infestation in the tank.

One thing to look out for is constipation. Many new aquarists notice this problem in their Swordtail fish. Untreated, long-term constipation might lead to swim bladder disease or intestinal blockages in fish. The issue arises when the fish consume too much protein and not enough fiber from plant sources. You’ll have to ensure the fish receive a well-balanced diet.

Breeding: Swordtails don’t need any assistance to breed. If you have males and females in the same tank, they will likely reproduce. Females can give birth to around 80 fry after each pregnancy. Swordtails also have a remarkably short gestation period of just 28 days.

– Guppy Fish

Adult Size: Guppies reach an average adult size between 1.1-2.4 inches. Male Guppies grow up to 1.2 inches at most, and females are on the higher end of the scale. It takes six months on average for juvenile Guppies to reach full adult size.

Tank Space: Guppies are sociable and must be kept in groups of at least three. Luckily, they’re also one of the least space-intensive species. You’ll do fine with just 5 gallons of space for a trio of Guppies! You should provide one extra gallon of water for every additional Guppy beyond that.

Water Parameters: Guppies need temperatures between 74–82°F, 6.8–7.6 pH, and 12–18 dGH. This translates to warm, mostly neutral pH, hard water. As you can see, Guppies are a bit more demanding than other livebearers, as they tolerate narrower ranges of parameters.

Tank Setup and Maintenance: Guppies are easy to house, as they don’t need a complicated setup. You won’t need aquarium lights, plants, or a top lid. However, Guppies still appreciate hiding spots and play opportunities.

Including a few live plants, caves, rocks, and other decorations will only help them feel at home. You’ll also need to invest in the essentials— a water heater, filter, and air stone. Any small hang-on-back filter will do if you have a small tank.

Guppies don’t produce much waste, especially if you only keep a small group. However, they still require regular water changes and tank cleanings, like any other fish. One medium water change (around 25%) each week, plus monthly siphoning and tank cleaning, should suffice.

Feeding: Guppies are true omnivores. They need a balanced diet that includes both proteins and plants. Feed them a combination of high-quality flakes, algae wafers, and freeze-dried or live invertebrates (bloodworms and brine shrimp are their favorites).

As for feeding frequency, you should feed them once or twice a day. Just know that Guppies are ravenous eaters and will consume as much as you give them. To avoid bloating and overeating, only feed them as much as they will finish within one minute.

Health: Guppies are small, but they’re pretty hardy. They aren’t predisposed to any severe illnesses. Like for other livebearers on this list, your primary concern should be avoiding infections. The most common infections in Guppies include ich, fin and tail rot, and protozoan disease. You shouldn’t worry about these diseases as long as you maintain a clean tank and stable water quality.

Breeding: Here comes the fun part. Guppies are perhaps THE easiest to breed species in the aquarium hobby. They’ve even earned the title of “millionfish” for that reason. Male Guppies, in particular, are known to pester female fish in the tank. They’re always ready for action, to say the least.

And did you know that one single female Guppy can give birth to up to 200 fry at once? Of course, that’s one of the extreme situations and would only happen if you are unlucky (or lucky, depending on how you look at it).


All of these livebearer species make great choices for beginner aquarists. These fish are equally peaceful, hardy, and have similar dietary requirements. However, I recommend choosing Platies over the other species. And there are a few reasons why.

Platies combine all the pros of other livebearer species and have the least cons. This makes them a low-maintenance but very rewarding pet to keep. Platies are quite small compared to Mollies and Swordfish. Thus, they require minimal aquarium space.

They aren’t as small as Guppies, but another significant advantage is that they don’t overbreed. They don’t produce as many fry as Guppies, and they have a slightly longer gestation period. Besides, male Platies are less likely to seek female fish 24/7, unlike Guppies.

Finally, Platies are hardy and easy to care for. They tolerate a wide variety of water parameters, especially water hardness. Platies don’t produce a lot of waste, so you won’t have to worry as much about tank maintenance. They aren’t prone to diseases and don’t need a special diet because they will eat anything you offer.

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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