Platy Fish: Aquarists Care Guide

Platy fish are hardy, easy to take care of, colorful, active and you have a huge variety of colors to choose from.

They’re a great fish to own, and in this guide, I’ll teach you how you can provide the best care for play fish.

Platy Overview

  • Care Level: easy
  • Temperament: peaceful
  • Size: 2.5-3 inches (6-8 centimeters)
  • Diet: omnivore
  • Minimum tank size: 10 gallons (38 liters)
  • Origin: Mexico and Central America
  • Temperature: 70°-80°F (21°-27°C)
red platy fish

Species 

The main types of platy fish that are available in the aquarium trade today are actually hybrids of two closely related species: the southern platyfish (Xiphophorus maculatus) and the variatus platy (Xiphophorus variatus).

The two species have been interbred for many generations in the aquarium trade. At this point, it’s almost impossible to tell the two apart since any tank-bred fish was likely hybridized at some point.

In the Wild

Platies can be found in rivers, canals, marshes and warm springs. They inhabit waterways with sandy or silty bottoms and live in areas of dense vegetation, darting in and out of plants to find food and avoid predators. 

Their native waters are somewhat hard and alkaline.

In contrast to the rainbow of bright colors you see in the aquarium trade, their natural coloration is pretty drab. They’re an olive green with some dark marbling. 

All the flashy colors you see in the store are thanks to many generations of selective breeding.

Appearance 

Platies are small fish that only reach a maximum length of about 3 inches (7.5 centimeters).

wagtail platy fish

They have a very pointed nose, large eyes and a rather thick body from their noses to their dorsal fins. Their bodies taper down towards their tails, making them very distinct from their abdomens. They have small dorsal, anal and caudal fins and a fan-shaped tail.

They’re very cute and inquisitive looking. Almost like you made a cartoon version of a fish come to life.

You have a huge variety of colors to choose from when it comes to platy fish, which is one of my favorite things about them.

They come in yellow, orange, blue, white and red. 

On top of that, they have many different patterns to go along with all those colors:

  • Wagtail – black fins and tail
  • Variegated – black blotches on the body
  • Twin bar – two black edges on the tail
  • Tuxedo – black on entire back half of the body with a different color on the front of the body
  • Mickey Mouse – three spots just before the tail that look like…well…the Mickey Mouse symbol

I’ve kept pretty much all of these. My favorites were always the wagtail and the Mickey Mouse. 

But that’s just me.

How to Set Up a Platy Fish Tank

Let’s run through the equipment you’d need to set up your own platy fish tank.

yellow platy fish

Heater

Platies originate from Mexico and Central America, so they require warm temperatures between 70° and 80°F (21°-27°C).

You’ll need to add a heater to your tank in order to provide them with the temperatures they need.

Pro Tip: Keeping the temperature stable in your aquarium is an absolute must. Rapid temperature swings are extremely stressful for fish.

The Nitrogen Cycle and Filters

It’s just a matter of fact, fish poop and pee in the water around them. 

I know, gross, but also true.

All that waste starts to accumulate at the bottom of the tank and break down. As it does, it starts to put off ammonia (NH3).

Ammonia is really quite poisonous, even in fairly small amounts. Left alone, it can build and build in the tank until it makes the water so toxic that it will kill any fish in the tank. 

So how are fish tanks even possible? If fish are constantly putting off waste into the water, how do they not die from all the ammonia?

The answer is the nitrogen cycle, a natural process that detoxifies ammonia, transforming it from a highly toxic substance to something fairly benign.

What causes this transformation?

There are beneficial bacteria that live in the filters and substrate that break down ammonia. They’re pretty much the only reason keeping fish in aquariums is even possible. 

Otherwise, we’d have to swap out 100% of the tank water every day. That would be a serious pain in the butt.

Not even I’m that dedicated to my fish.

There are actually several different kinds of beneficial bacteria in aquariums. One kind eats ammonia and puts of a substance called nitrite (NO2 -1). Nitrite is also very toxic but another kind of bacteria eats it up rapidly and turns it into nitrate (NO3-). 

Nitrate is much less toxic and can be allowed to build up in the water in between weekly water changes.

Pro Tip: The bacteria that you need to process ammonia don’t show up in your tank instantly when you set it up. It takes time to get them to colonize your filter.

For more in depth information about the nitrogen cycle, including how to get the cycle going in your tank before you even add fish, see our complete guide here.

Since the majority of the beneficial bacteria in your tank live in your filter, it’s important to make sure that you get one big enough for your tank.

It’s always better to over filter than under. 

I also recommend that you go with a filter that has a large capacity for biomedia, the kind of filter media that beneficial bacteria live on.

Filters that run on cartridges just don’t hold much biomedia. Plus, you lose beneficial bacteria any time you switch out the cartridge. 

I like Seachem Tidal or AquaClear filters since they have so much room for biomedia. You can fit more than twice as much biomedia into one of these than a filter that uses cartridges and it never needs to be removed, so you don’t lose any of your beneficial bacteria.

Substrate 

Platies don’t really have particular substrate needs. 

They will swim along the bottom sometimes, but they really don’t interact with the substrate.

So gravel, sand, bare bottom, go with whatever you prefer. The fish really won’t care.

Plants and Decorations

Platies love plants. Having densely planted areas in the tank mimics the habitat where these fish live in the wild.

Dense planting also gives fry a place to hide from marauding adults bent on eating them.

A mix of planted areas and open swimming areas works best. 

They don’t need things like caves to hide in, but they will dart through holes in decor in a way that is really cute and entertaining.

Related: Best Aquarium Plants For Beginners

Water Parameters

  • Temperature: 70°-80°F (21°-27°C)
  • Ammonia/Nitrite: 0
  • Nitrate: <30 ppm
  • pH: 7.0-8.0
  • GH: 10-28 dGH (167-467 ppm)
  • KH: 3-5 dKH (54-90 ppm)

Platies originate from tropical waters that tend to be a bit on the harder side and have a slightly alkaline pH.

But, they’ve been tank bred for many, many generations and are pretty flexible when it comes to water parameters. They can adapt to softer or harder water with the proper acclimation.

Diet and Feeding

In the wild, platies are omnivores. They will graze on algae and plant material they find as well as eating insects, larvae, fish eggs, fry and any other small critter they can find.

I’ve never known them to be picky eaters. They’ll gladly accept flake, micro pellets, frozen food and freeze dried foods as well as live foods like daphnia.

They are voracious eaters that will swarm from all over the tank as soon as you put food in the water.

You know how sharks go into a feeding frenzy as they devour some unsuspecting victim?

It’s pretty much like that. Just smaller and way cuter.

If you have a really big school, or if you have slower fish in the tank with them, you might want to put food in several places around the aquarium to make sure everyone gets something to eat.

Make sure to give them a staple diet made from high quality ingredients like whole fish or shrimp.

They also need some plant matter in their diet so look for ingredients like spirulina, kelp or algae meal.

It’s always a good idea to give fish a varied diet to make sure they get all the nutrients they need.

Tank Mates

Platies are very peaceful little fish that can be safely mixed with other small community fish.

They could easily live with species like:

Tank Mates to Avoid

It can be a problem to mix platies with other livebearers like guppies and swordtails.  

Males from other species will harass female platies trying to mate with them.

Definitely avoid any fish that is listed as aggressive or semi-aggressive, platies just can’t hang with the bad boys. Pushy, nippy fish like barbs and cichlids should not be mixed with platies.

Any fish that gets over 4 inches (10 centimeters) long should be avoided to prevent the platies from being bullied.

Breeding Platies

Breeding platies couldn’t possibly be easier. 

It would be way more of a challenge to not breed them.

Just add water and they’ll gladly have a million babies for you.

But seriously, it really is very simple to breed these little guys.

Platies are livebearers and will breed readily. Females give birth to 20-50 babies at a time. They will produce a new brood about every 4 weeks, depending on the water temperature (the higher the temperature, the faster they breed).

How to Sex

Sexing platy fish is fairly easy.

Male platies have a pointed anal fin that points straight back at their tails. It looks very different from the pelvic fin that grows just before it on the fish’s belly.

Females have a much more rounded anal fin. It looks like an exact copy of the pelvic fin.

Also, females have a rounder, thicker body, making the males look more slender. But, this can be kind of subtle if you haven’t been around them for very long.

Pro Tip: When buying platies, you should keep one male for every three females. Male platies will constantly go after females trying to mate. Having more females to males makes sure no one female is harassed to the point of being stressed.

Raising Fry

Livebearers already give birth to free swimming fry. So there’s no need to worry about guarding eggs or making sure that they don’t get moldy.

The biggest thing is to protect the poor little baby fish from the ravenous horde of adults. 

It’s gotta be tough growing up in a family where your auntie might eat you at any second.

There are two ways to protect the fry so you can raise them:

  • Breeding box – when females look like they’re about to burst, put them in a specialized breeding box so they can give birth and keep the fry away from other fish. Once she’s had the babies, move them to another tank for raising. They can be moved back once they reach an inch in length and can’t be eaten.
  • Lots of cover – if your tank has densely planted areas, especially large clumps of Java moss, the fry will instinctively hide out in them. They’ll happily munch on algae, aufwuchs and little bits of uneaten food while they grow to size. Some will get picked off by adults, but most will make it to adulthood. 

It’s best to give fry a prepared food meant for them. This ensures that the food is small enough for their tiny mouths and that it gives them all of the different nutrients they need to grow.

Final Thoughts on Platies

In case you can’t tell, I really love these little fish. My son’s first fish tank had a big school of platies and we really enjoyed them.

They’re hardy and easy to take care of, they’re colorful, active and you have a huge variety of colors to choose from. Plus, platies are also just downright adorable.

You don’t need a huge tank or an elaborate setup to keep them. I think they’re a great choice for beginners.

They make an awesome community fish that can be mixed with almost any other small, peaceful fish.

I highly recommend this species. A platy tank is never boring. You can spend hours watching them dart around the tank and play.

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