What comes to mind when you think ‘guppies’? Perhaps it’s brightly colored males displaying flashes of kaleidoscopic colors on their long, flowing fins. Maybe it’s chubby pregnant females bobbing about in all their boxy glory. Or even hordes of hungry fry that ravenously attack flake food with the ferocity of Jaws and the pack mentality of piranhas. If you’ve kept them recently, you’ll likely think hunched backs, diseases, and premature death. Grizzly scene? No doubt, but it’s the current one.
Recent keepers of guppies will attest that most are not as hardy or robust as they used to be even 10 years ago. Over farmed, inbred, and prone to disease, guppies are not the beginner fish they once were and are now more suitable for experienced hobbyists.
Guppies, although often looked down upon by more experienced keepers, have their place in scientist’s hearts. They have distinctive personalities. Or, more accurately, their own distinctive mechanisms for dealing with potentially life-threatening situations. They’re also capable of rapid evolution – as little as 11 years – which is much faster than science initially thought animals could evolve based on fossil records. In addition, they show interesting forms of communication, display a unique link between “friendship” and predation, and as it turns out guppies are smarter than we’ve ever imagined. They also have a rather interesting survival strategy.
One would assume that being diminutive and delicious would mean that you’d want to hide to avoid predation. But guppies never seemed to get that memo, displaying bright flashes of greens, blues, and oranges in the wild and, in fact, female guppies have shown to favor the most colorful males. As it turns out, being a tiny neon dinner sign means you must be smart, quick, and strong to avoid being eaten – so being colorful and surviving in the wild is the ultimate testament to how great their genetic material is.
For beginners, we suggest avoiding these beautiful scientific marvels and instead consider endlers or gambusia, both of whom being more robust. Better yet, start with some true beginner fish or community fish. But if you’re up for more of a challenge (although not a huge one,) here’s what you need to know about keeping guppies.
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Table of contents
Why do my guppies keep dying?
Again, guppies are not what they once were, and absolutely require a mature cycled tank prior to being added. If that’s in order, then it’s likely deteriorating water quality, low oxygenation levels, or simply stress. Stress for guppies can come from many avenues such as temperature, lack of hiding places, harassment from males, complications in pregnancy or delivery, or tank mate incompatibility.
How can I tell if a female guppy is pregnant?
Almost all female guppies are always pregnant from a few weeks old, but pregnancy is usually more obvious towards the end of gestation in larger guppies. If she is pregnant, there will be a dark almost black dot above her pelvic fin that gets larger and darker with time, if you look closely, you may be able to see baby guppy eyes. A few days before birth she’ll get “boxy looking” and more “squarish” as the babies drop into place for delivery.
How many guppies can I keep per gallon?
With a minimum suggested tank size of 10 gallons, 10 adults would be the maximum I’d suggest for a well-cycled guppy-only tank for a beginner. But it’s important to keep in mind that you want way more females than males, I suggest 4 females to 1 male minimum, so you’ll likely exceed 10 guppies quickly! If you’re more experienced, colonies are certainly obtainable in 10 gallons so long as you keep the male population down to prevent stressing the females. 20-gallon or larger colonies are certainly much easier to maintain and are an arguably more impressive sight.
Class: Actinopterygii are ray-finned fishes, which is a subcategory of boney fishes. These fish are characterized by the bony structures that support their webbed fins. This group makes up nearly half of all living vertebrates.
Order: Cyprinodontiformes is an order of ray-finned fishes that consists of mostly small, freshwater fish, and includes killifish and livebearers.
Family: Poeciliidae, even though the whole family is known as “live bearers,” there are some fish in the family that are eggs scatterers who utilize external fertilization.
Genus: Poecilia consists almost entirely of mollies – except for Endler’s livebearers (P. wingei) and guppies (P. reticulata.)
Scientific name: Poecilia reticulata
What Does Poecilia reticulata Mean?
Poecilia means “many-colored” and reiculata means “net-like” in Latin.
The wild fish that was found over 100 years ago was certainly a different looking fish than the ones we can buy today, which is why the name sounds a touch misplaced. They looked much closer to endlers (perhaps even indistinguishably so.) However, being as inbred and line bred as they are now, even the early developmental stages of modern guppies look strikingly different from their wild counterpart.
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Wild Habitat & Distribution
Guppies are widely distributed in Southern and Central America, specifically Venezuela, Barbados, Trinidad, Brazil, and the Guyanas. Wild specimens are incredibly adaptable and can live in nearly every biotope from ditches to brackish waters. They’re so adaptable, in fact, that they’ve been introduced to other river, ditches, and lakes around the world for mosquito control (and likely by reckless hobbyists.)
Recently, scientists have been arguing that not only are guppies and similar mosquito munching livebearers not proven to be effective at mosquito control, but they’re so prolific that they pose real danger to indigenous wild fish and can be an invasive species. You don’t get named the “million fish” by not living, sleeping, and breathing reproduction!
“It all sounds like it’s magical—you put the guppies in, they eat the mosquitoes, everything is fine, our concern is that you have a potentially invasive species that is being introduced haphazardly.” Says Rana El-Sabaawi, an ecologist and lead author on the invasive species paper.
Some studies show guppies are sexual harassing a threatened species. While the headline may be comical on face value, the threat that guppies pose to biodiversity is no laughing matter. The mating of guppies is a painful affair as the gonopodium of male guppies is believed to be hooked and, after removal, causes inflammation that locks in sperm. How this affects Skiffia bilineata’s reproduction long-term is still largely unknown, but it’s no doubt a painful and stressful affair for the unsuspecting female skiffia. Beyond the skiffia, there are numerous studies from Hawaii [1 2 3 4] that all point to reduced biodiversity of both vertebrate and invertebrate species in Hawaiian waters at the hands of guppies.
While it might be tempting to paint guppies as the villain in this portrait, it’s worth keeping in mind that they’re just utilizing their survival strategy, which is a brilliant one at that. Without this ability to rapid-fire reproduce they wouldn’t have been able to adapt so quickly or keep their numbers high enough to survive in their native waters. It’s humans that are to blame for the success of guppies as invasive species and it’s worth reading about how to properly rehome you fish and what to do with dead fish to prevent additional invasive species and diseases spreading to native wildlife.
Size: 2.5″ (6 cm)
Lifespan: 1.5 – 2 years
Tank Size: 10 gallons (40 liters)
Diet: Omnivore – will eat prepared foods
Temperature: 76 – 82F (24 – 27C)
Guppies should, bare minimum, be kept in a 10-gallon tank with plenty of their own kind. This often comes as a surprise to many guppy owners, but guppies are social fish with incredibly complex hierarchies. From the outside looking in, the subtleties in these hierarchies are hard to see because guppies use methods of communication that (usually) don’t involve violence to establish dominance. While, yes, fin nipping and chasing can be common, those signs are usually less frequent than the plethora of other mechanisms guppies use to assert dominance. Often violence is displayed when social cues and manners are ignored – usually by budding males or species of fish that don’t speak guppanese.
A well cycled and mature tank with hard water is a must with these fish. Aside from a heater and filter of some sort, they’re not picky. Unlike some fish that are spooked by neon pink rocks, guppies don’t seem to care. Plants or no plants simply comes down to a matter of if you want to see fry without intervention and what other species you chose to house guppies with.
Guppies are wholly unfussy omnivores when it comes to chow. A sure sign of a sick guppy is refusing food that’s offered, so observed them eating before purchasing them if you can.
They’ll happily accept flakes, micro pellets, freeze dried bloodworms, Repashy, and basically anything else you plop into the tank that fits in their mouths – including their offspring! Guppies are also known to munch spinach, zuccunni, green beans, peas, and other vegetarian fares. This works out great if you keep them with shrimp or plecos.
Additionally, like all fish, they benefit from live food. Breeders often feed baby brine shrimp, daphnia, grindal worms, white worm, or fruit flies to their gups. Luckily these live foods are easy for the average person to culture. Fry are similarly indiscriminate with food, eating anything that will fit in their mouths. At small sizes this includes infusoria, awfuchs, powdered Repashy, baby brine shrimp, and finely crushed flake food – among other options.
Common Guppy Diseases
Guppies are susceptible to basically all tropical freshwater fish diseases. The most common, however, include ich, velvet, and fungal infections. They’re also prone to scoliosis and fish tuberculosis (TB,) so understanding how to properly quarantine, diagnose, and treat fish is generally helpful. Some things, like scoliosis and TB are untreatable, and it’s best to euthanize suffering fish as humanely as possible. Ultimately, how and when is up to you, but we hope this useful guide on euthanasia and suffering fish is a helpful place to start thinking about when, how, and if it’s right for your situation. And, again, read up on how to properly dispose of dead fish to avoid spreading pathogens to local waterways and native fish!
Fungal infections are a tricky bunch – not only do they have a huge family that presents a wide variety of species and symptoms – but some bacterial infections look strikingly similar to a fungus.
If you’re not sure if you’re dealing with a fungus or a bacterial infection, I find it helpful to treat with Ich X and Erythromycin (provided it’s 100% erythromycin) at the same time to be sure I’m treating for both.
- Cottony growths on body, fins, eyes, and/or gills
- Prior untreated injury
- Water quality-related issues
- Prior untreated infection (bacterial, parasitic, etc.)
Ich (White Spot Disease)
Ich is caused by a parasite that, to many, looks like tiny white pimples across the fish. It can attach to the mouth, fins, body, and gills. You can usually see fish scraping themselves against objects (likely because parasites are itchy!) before white spots even appear.
- White spots
- Redness or bloody streaks
- Ichthyophthirius multifilis (parasite)
Velvet (Gold Dust Disease)
For whatever reason, bettas are particularly prone to velvet, but any tropical fish can get it. Velvet is caused by a surprisingly attractive-looking parasite that can easily go unnoticed until the fish dies from them.
Symptoms, not unlike ich, include itchiness, lethargy, rapid breathing, clamped fins, and obviously a gold dusting. Treating velvet can be done the same way that you’d treat ich.
- Brownish/gold discoloration
- Clamped fins
- Skin peeling off
- Labored breathing
- Oödinium pilularis (parasite)
Fish Tuberculosis (Fish TB)
Fish TB, or mycobacteriosis, is a zoonotic disease, meaning you and your family could contract it from a fish, and there’s a slight (although rare) possibility you could pass it to your other pets such as your cat or dog.
Although contracting fish TB yourself is highly unlikely, the disease is (as far as we know) uncurable and it’s best to remove the affected fish to a new tank and euthanize it appears to be suffering. If it’s not suffering, you can likely wait it out if you feel like it (although safety precautions are recommended!)
- Wasting of flesh and muscle tissue
- Spinal deformities
- Missing scales
- Severe abdominal bloating and fluid retention
- Several mycobacteria are known to cause this; M. fortuitum, M. flavescens, M. chelonae, M. gordonae, M. terrae, M. triviale, M. diernhoferi, M. celatum, M. kansasii ,M. intracellulare, and M. marinum.
- Research indicates all fish are susceptible to fish TB, but these mycobacteria grow more readily at 77 F (25 C) and up beyond normal water temperatures, they’re more frequently encountered in tropical fish.
Contrary to popular opinion (and practices) guppies don’t make ideal community tank inhabitants. Going over the list of the usually recommended suspects should help shed some light on this. Corydoras? It’s possible, but not an ideal. Guppies are livebearers that want hard water while corys want softer water – although they can be kept in moderately soft, it’s not great for them and the reverse is true for most corys. Neon tetras? Again, possible, but they prefer soft water and are notoriously fragile now. Clown loaches get massive and require a huge tank and a large school. Wrestling halfbeaks are easily spooked and could easily starve to death with such boisterous tank mates gobbling up the lion’s share of food. White clouds, yes, have most overlapping pH and dH ranges, but they prefer cold water, which guppies will usually fall apart in.
So what can you keep with a guppy?
There’s not many nearly-no-fail options, but here are a few you could certainly consider with a relatively high degree of success:
Bolivian Ram (Mikrogeophagus altispinosus)
The underrated cousin to the German Blue Ram are often nearly colorless and shy in the store tanks. But provided with the right tank and dither fish, they’ll color up and exhibit fascinating behavior in your home aquarium!
Keep in mind these rams will also become territorial while spawning. However, there are some sparse reports of other tankmates going unnoticed during spawning.
pH: 6.0 – 7.5
dKH: 1 – 10
Temp: 68 – 83 F (20 – 28 C)
Size: 3″ (8 cm)
Swimming: Bottom to mid-water
Sparkling gourami (Trichopsis pumila)
Little known fact about sparkling gouramis; they’re quite social and gregarious creatures! Although they don’t school or shoal, they do enjoy social interactions with their own kind – in fact, most gourami do! – and we suggest a four minimum to make sure they’re comfortable.
pH: 6 – 8
dKH: 5 – 18
Temp: 72 – 81 F (22 – 27 C)
Size: 1.5″ (4 cm)
Temperament: Peaceful, can be aggressive when spawning
Swimming: All water
Cherry Shrimp (Neocaridina davidi)
Neos enjoy munching on decomposing plant matter, grazing on algae, and picking sunken pieces of wood and plants clean. This makes them a perfect addition to a naturalistic tank. They come in a variety of colors including the oh-so-common cherry shrimp!
pH: 6.5 – 8.0
dKH: 8 – 20
Temp: 70 – 79 F (21 – 26 C)
Size: 1.6″ (4 cm)
Swimming: Anywhere there’s food to pick, but usually bottom
Bristlenose Plecos (Ancistrus sp.)
Most plecos aren’t suited for the average aquarium, some growing up to two feet long – not the bristlenose pleco. They’ll happily munch on algae, green beans, zucchinis, cucumbers, sinking algae wafers, and of course leftovers and fish poo – although leftovers and poo make for a literally shitty diet.
pH: 6.0 – 7.5
dKH: 6 – 10
Temp: 60 – 80 F (15 – 27 C)
Size: 4 – 5″ (10 – 12 cm)
Temperament: Peaceful, can be territorial
Swimming: Everywhere that has structure
Nerite Snails (Neritina natalensis)
The most common complaint about snails is that they can reproduce like crazy, this is especially true for tanks with tons of leftovers! Nerite snails, however, can’t reproduce in freshwater so this isn’t a concern for the average aquarium. A simple remedy to keeping shrimp in soft water or water with little calcium is to add Tums to the tank for them to munch on to get their calcium fill.
pH: 7.0 – 8.9
dKH: 6 – 12
Temp: 70 – 80 F (21 – 27 C)
Size: 1″ (2 cm) although somewhat species dependent
Swimming: Everywhere there’s food
Realistically, you could combine all above species in one tank provided it was large enough and you’d likely see some breeding activity so long as they were all housed properly. Endler’s, on the other hand, have a lot more going for them if you’re willing to give them a go in a community tank of miniatures.
Keeping guppies from breeding is much harder than breeding them. If you own guppies, fry are almost certainly part of the territory. Even if you buy a single female guppy, you’ll likely have fry for months as female guppies can store sperm for future pregnancies. They’re a “just add water” kind of fish.
There are two basic ways to breed guppies, here’s how to do it:
Colony Breeding Guppies
You can, of course, leave the fry with the parents. You’ll likely get quite a few fry still provided there’s enough cover for them to hide in. This can come in the way of plants, rock piles, spawning mops, leaf litter, terracotta pots, or mesh cylinders to keep the fry and parents separated.
Another method is to separate the tank with a mesh divider large enough for fry to swim in and out of, but not the parents. If you densely plant one side while leaving the other bare, fry will naturally flock to the cover where you can later net them out when they’re big enough to live with adults.
If going with this method, it’s wise to feed the tank as if there are always fry present as you’ll likely never see them.
- Not a ton of babies (this may be a con for some, but not most.)
- There’s some small form of natural selection happening where the weaker fish aren’t being “saved” on the part of the breeder.
- It’s easier to maintain since there’s no catching pregnant females, shuffling fry from tank to tank, or maintenance of more than one tank.
- Economical in terms of time, space, and money.
- You can make it “pretty” (whatever that means to you) since you needn’t be netting adults out every week or more.
- Your tank can still quickly become over run.
- You’ll likely need to separate young and mix new blood in to prevent inbreeding.
- Lower control over genetics in the tank.
Raising Guppy Fry Away From Parents
There are, similarly, a few ways to achieve this. You can net out pregnant females and put them in breeder traps until they drop their fry, at which point you can put mom and babies in their respective homes. You can also simply plop the female in a smaller tank (say 5 gallons) where you can raise up individual batches of fry and simply net out the mother after she gives birth. You can also keep the fry in the parent’s tank in a breeder trap.
The old-school way of doing this is with a bare breeding tank containing only pile of rocks and an airlift tube connecting to a second tank. The idea is that fry will seek cover after birth and the only cover will be the pile of rocks where adults can’t reach them. Inside the pile of rocks is the airlift tube that will suck up the tiny fry and spit them into the connecting tank where they’ll be safe from harm. From this second tank you can pick out larger individuals who will be safe with their parents but present a risk to the smaller fry. This method has a lot of pros, but also comes with the con that you need to be handy, or at least know someone who is, to pull this off.
How To Stop Guppies Breeding
There’s one of six ways you can accomplish this, only half are realistic for the average accidental guppy breeder.
- Keep only males, whom will no doubt squabble. It’s best to keep so many males that no one male can be truly dominant. This is tough even in larger tanks.
- Keep only females. This poses a few problems because, again, female guppies can store sperm for up to six future broods – possibly more! Without the presence of male harassment, her batches will likely be larger. This almost creates more of a problem in the meantime and you’d have to wait at least six months before you’d likely see no fry. Of course, you’d have to separate all the fry from the parents as well to prevent sons and nephews from continuing the cycle. This is almost pointless given the short lifespan of guppies and the fact that most people don’t keep guppies for the looks of the females.
- Buy virgin females. This is tricky since guppies start breeding at around a month old given the opportunity. If fry aren’t separated properly, one rouge sneaker male could spoil the whole lot. Virgin guppies are also difficult to source and are incredibly expensive for that reason alone, plus they’re highly sought after by serious guppy breeders. And, again, females aren’t usually what guppy keepers want in their tanks.
- Breed virgin guppies. Provided you can accurately sex guppies, you can keep your own fry separated from a young age and might be successful in breeding guppies who will never breed themselves. Any excess virgin females can be sold for a pretty penny providing they’re a pure, quality, strain. Of course, this method is difficult. If it were easy to do, there’d be more of them on the market.
- Don’t keep guppies. This is hands down the easiest, cheapest, and least headache-ridden way to stop guppies from breeding in your tanks. Probably not the advice you wanted to read, but there it is. This isn’t to say I dislike guppies and think they’re not worth breeding. Like many, my first fish love was guppies. But if you don’t want to be overrun or run into headaches with male-only tanks, it’s best to not tempt fate at all, is it not?
- Keep them with other fish that will eat the fry. Maybe this sounds cruel, but keeping guppies with fish that will eat their fry is probably the easiest way to prevent being overrun. In a sparsely planted tank with a few guppies and some other fish, it’s unlikely most of the fry will survive – although you’ll likely still see a few.
Further Reading & Resources
Seriously Fish – Poecilia reticulata
Animal World – Guppies, Poecilia reticulata, Fancy Guppies
Washington Post – Scientists spent a month terrifying guppies to prove that fish have personalities
Guppy Evolution – The science behind Guppy Guppy Evolution
Science Mag – When they’re on the attack, guppies’ eyes turn black
ScienceDaily – Predator threat boosts friendships among guppies
HuffPost – Brain Size Study Involving Guppies Suggests High Intelligence Comes At High Cost
The Royal Society – Biodiversity and ecosystem risks arising from using guppies to control mosquitoes
NewScientist – Guppies sexually harass threatened species