Platy FAQ

  1. aylad Well Known Member Member

    Maybe it's just me, but there seems to have been a rush of platy-related questions pop in the last couple of months, with special emphasis on pregnancy and fry. I figured I'd have a stab at creating a FAQ to answer some of the most popular questions. I hope this will be useful to someone.

    Most of the material here is from personal experience or from bits and pieces I've seen around the FL forums. I didn't cite any sources because they're either first-hand or tidbits scattered far and wide in posts here. None of it comes from other websites, however.

    These are my thoughts on platies. Your mileage may vary.

    Remember that FishLore has a Platy Profile.

    To quickly skip to a specific question, press Ctrl+F and search for the question number (Ex: PF-8)

    PF-1. Is my platy pregnant?
    PF-2. When will she drop her fry (give birth)?
    PF-3. How many fry will she drop?
    PF3b. How long will it take?
    PF-4. Will the other fish eat her fry?
    PF-5. That's awful! How can I protect the fry?
    PF-6. What other dangers will my fry face?
    PF-7. How do I feed my fry?
    PF-8. Help! My platy gave birth early and I hadn't put her in the breeding trap yet!
    PF-9. How soon can I put them with the adult fish?
    PF10. How long will it take them to reach maturity?
    PF11. How can I stop my platies from breeding?
    PF12. Is my platy male or female?
    PF13. Can platies and ________ interbreed?
    PF14. Are platies schooling fish? Do they need company?
    PF15. So I have a platy in my 5-gallon tank, and...
    PF16. Is a 10-gallon tank really big enough?
    PF17. I see platies nibbling at my plants. Are they eating them?
    PF18. About that... they ALWAYS seem hungry!
    PF19. What are appropriate tankmates for platies?
    PF20. What pH do they need?
    PF21. I see photos online of platies proudly displaying their fins, but mine hold their fins close to their bodies.


    PF-1. Is my platy pregnant?

    Yes. Easy question. If the following are all true, she is most likely pregnant:

    1. She has been in a tank with a male platy or swordtail within the last 6 months.
    2. She is an adult, more or less (rough estimate, maybe 3/4 of an inch long).
    3. She is a she. See the "is my platy male or female" question for reference.

    PF-2. When will she drop her fry (give birth)?

    Platies normally stay pregnant for roughly a month. Having said that, the water chemistry and temperature in your tank may shorten or extend the pregnancy, and if she is heavily stressed out due to the water chemistry, incompatible tankmates, or similar reasons, she may terminate the pregnancy.

    If you don't know how long she's been pregnant, it's not always easy to give a simple answer to this question. The classic sign is a large, dark "gravid spot" (Google it) above and slightly in front of her anal fins; she may also "square off," which means to have a somewhat square-shaped belly. Younger platies, however, may not square off noticeably, and certain color patterns may make the gravid spot harder to see.

    In any case, if she squares off, she's ready to start dropping fry any second now. If the other fish are chasing her around the tank, she may already have started giving birth. When her fry start dropping, the other platies will tend to see her as a vending machine with fins, dispensing free snacks. See "will the other fish eat her fry" below.

    PF-3. How many fry will she drop?

    Again, it's hard to say, because depending on her age, health, water conditions, how many times she's given birth, etc. etc. etc., it may be 3-4 or 30-40.

    PF3b. How long will it take?

    It's probably no surprise by now that I'm going to answer: hard to say. See the above question... it should take longer for more fry, and other factors will have an effect as well. I'd say leave mom in the breeder for 6-12 hours, although she probably won't take that long.

    If your breeding container doesn't separate mom from the fry, she might be able to eat some of her little babies during this time period (I've read that she won't eat them for a few hours after giving birth, but I have seen a platy swallow a fry IMMEDIATELY after birthing it. Its total lifespan was less than 5 seconds). If you see as many fry in the breeder as you want (or can take care of), go ahead and move her back into the tank. If you miss a couple, well, she'd probably have eaten at least that many anyway.

    See question PF-5 below.

    PF-4. Will the other fish eat her fry?

    Yes, absolutely. Few fish will be able to resist the sight of a fresh, juicy fry swimming past their noses. Even the mother will eat her own young.

    PF-5. That's awful! How can I protect the fry?

    If you want to save as many as possible, invest a few dollars/euros/whatever in a breeder box or breeding net. Read the directions and use it as directed. The general idea is that the mother is placed in the breeding trap, she gives birth, she is removed, and the fry are kept inside until they are big enough to fend for themselves (in a platy-only tank, this may be as brief as a couple of weeks).

    If you want to do things the "natural" way, just have lots of hiding places where the fry can go to escape the other fish. This is probably your best bet if you don't have the tank space for dozens of platy adults.

    PF-6. What other dangers will my fry face?

    Filter intakes, larger fish, gravel vacuums, poor water quality, some species of invertebrates, starvation... it's tough being a tiny tiny fish.

    Cover your filter intakes with a prefilter sponge (Fluval makes a nice one that fits on many of the most common filter designs, or you can search for instructions to DIY one). You can also use never-used and never-washed nylon stockings. Vacuum your gravel with care, or cover the end of the vacuum with a stocking.

    Larger fish and invertebrates, including (reportedly) ghost shrimp, crabs, and crayfish, are a threat, but hiding places or breeding traps can protect your fry from them. See the question above.

    Do water changes every day or every other day. This will prevent the accumulation of toxins in your water and also dilute fish hormones in the water that slow your fish growth rates.

    PF-7. How do I feed my fry?

    Normal flake food can be crushed up into a fine powder and sprinkled into the water. I like to put a pinch of food inside a plastic sandwich bag and work it between my fingers. This lets me crush the food into ever-smaller pieces without getting it all stuck to my fingers. This is not an ideal fry food, though. It works, but it may not have the nutrients that growing fish need.

    Special fry foods are available that are already tiny and nutritionally balanced for healthy fry. There are other options like baby brine shrimp that may interest you as well.

    If your fry are in a breeding trap, you may find that the food sits on the water's surface until it starts to look nasty. I have noticed that fry are often unwilling to come to the surface to eat, especially in the first few days of life. Try dripping a few drops of water onto the fry powder to break the surface tension and drive the food down into the water column. Your fry will be excited to eat food drifting past their faces!

    If your fry are not in a trap, sprinkle the food in front of your filter's outflow (if possible). This should drive the powder down into the tank and disperse it where fry can reach it from their hiding places.

    You will probably find that you are feeding much more food than they are eating, simply because they won't see the food if you only put in enough to fill their tiny bellies. Frequent cleanings are important to remove excess food buildup.

    They may not want to eat for the first 24-48 hours, but sprinkle a little food in, just so it's there when they're ready.

    Feed them 2-3 times per day.

    PF-8. Help! My platy gave birth early and I hadn't put her in the breeding trap yet!

    This has happened to me SO many times. You'll probably lose some fry to the bigger fish, but you can save others. You can use a turkey baster (never washed) to suck up fry and deposit them into the breeding trap. The hard part is sneaking up on them, but you'll get the hang of it. Just have a comfortable stool in front of your tank to sit on. ;)

    The first time I did this, I had a bubble wall on one end of the tank. When the fry swam into the bubbles, they were disoriented by the strange currents and struggled against the flow. They were very easy to snatch with the turkey baster that way. You might give it a shot if you are having trouble catching them otherwise.

    PF-9. How soon can I put them with the adult fish?

    They should be large enough to be left alone by adult platies around 2 weeks after birth. This is not to say that they're ready to be put in the main tank. Bigger fish might still go after them, and they may still have trouble swimming against the rougher currents outside the breeding trap. On the other hand, keeping 20 fry in a small breeding box is a situation you want to end as quickly as possible. Consider your tank environment and weigh your options.

    PF10. How long will it take them to reach maturity?

    That depends on the tank environment and available food. With frequent water changes and healthy, protein-rich food, they can grow fairly quickly; with less frequent water changes and lots of other fish in the tank, they will grow slowly.

    PF11. How can I stop my platies from breeding?

    I've got a deadly parasite in one of my tanks that apparently sterilizes the fish several weeks before it kills them. I don't recommend it, though.

    Seriously, though: Keep all males or all females. Be aware that an all-female tank may include females impregnated before you got them, and if they give birth to males, they can and will breed with their own offspring. Consider an egg-scattering species if you don't want fry. If you love your co-ed platy tank, just don't intervene with the fry... the adults will eat many of them, often leaving you with no surviving fry at all.

    PF12. Is my platy male or female?

    Look at the fins on the underside of their bodies near the tail. The female's fins are all fan-shaped, but the male has a narrow, pointy shape to his fins. Google "platy gonopodium" to see what this looks like.

    Also, check out FishLore's guide to sexing livebearers.

    I have been fooled by platies with clamped fins in dim lighting, but generally, once you know what to look for, you'll always know the difference.

    PF13. Can platies and ________ interbreed?

    Platies can hybridize with swordtails, but I am not aware that they can breed with anything else.

    PF14. Are platies schooling fish? Do they need company?

    They don't school or shoal, but they are very social. They do best if you have at least 3-4 platies, although other peaceful, social fish will provide company as well. Be aware that the male platies might try to breed with any similarly-sized fish you put in the tank with them. They aren't picky. Don't worry about weird hybrids, though... see the question above.

    At the same time, platies need privacy occasionally. Have hiding places in your tank so that they can get away from each other sometimes.

    PF15. So I have a platy in my 5-gallon tank, and...

    Stop. Stop right there. Go and buy a bigger tank, at least 10 gallons, then come back for whatever question you were about to ask.

    PF16. Is a 10-gallon tank really big enough?

    Well... yes. About 4, maybe 5 platies can live comfortably in a 10-gallon tank, if it's not crowded with other fish. Really, though, go buy a 20-long or a 29-gallon tank and watch how thrilled your platies will be to have more space.

    Please note that some platy owners believe platies need more than 10 gallons based on the amount of waste that they produce. While their experience has been a little different from mine, I agree that platies live better in larger tanks and I definitely recommend over-filtering your tank if you do have 4 or 5 platies in the tank. As of this writing, the 10-gallon tank that I keep 4 adult platies in has a TopFin 10 and an AquaClear 30 running side-by-side for a total of (if I remember the stats correctly) 200 gallons per hour filtration capacity. That's 20 times the tank volume, every hour.

    PF17. I see platies nibbling at my plants. Are they eating them?

    Nah. They're probably nipping at algae or something similar that you didn't want anyway. They won't actually feed themselves this way, but they do like to nibble algae when they're feeling a little peckish... which is ALL the time.

    PF18. About that... they ALWAYS seem hungry!

    Yes. They're like teenage boys. They'll eat anything and everything you can be persuaded to drop into the tank.

    This doesn't mean that you should feed them all they'll eat. Like teenage boys, overeating can be very unhealthy. Feed them as much as they'll eat in about 1 minute every day, and that's enough. Feed for 2 minutes if you're feeling especially generous, or if your platies seem to be getting a little thin. I wouldn't do that every day, though.

    Platies will try to rob slower fish of food, and algae wafers are platy magnets. They can actually harm themselves by gorging on algae wafers. Consider not housing them with fish or invertebrates that need wafers dropped in. (The usual rule of thumb is to drop the wafers in after dark for inverts and nocturnal species, but I've seen platies find and demolish algae wafers even in EXTREMELY dim light.)

    PF19. What are appropriate tankmates for platies?

    The FishLore profile says that they can be housed with similar-sized peaceful freshwater species, but I'd recommend not putting them with slow-moving fish (the platies can steal their food) or species that need algae wafers (which I've seen platies gorge themselves on, even to the point of self-harm). See the question above for my thoughts on that.

    This is a RECOMMENDATION, not a hard-and-fast rule. I wouldn't say it if I didn't believe it, but your experience may be different from mine. Observe and use good judgment.

    PF20. What pH do they need?

    Don't worry about it. Like most fish, they will adapt to whatever pH you have.

    PF21. I see photos online of platies proudly displaying their fins, but mine hold their fins close to their bodies.

    This is called "clamping" and indicates that your platy is unhappy. Usually, this means illness or poor water quality. You probably bought them from your pet store with clamped fins, and the first time you realize that they've all unclamped and are happy, you'll know that you've made a good home for your fish. ;D
     
  2. Donnerjay Well Known Member Member

    Holy cow! Thank you for your time and effort in creating this. Seems like once the moderators evaluate your work, they may "sticky" it for all to see. :)
     

  3. kinezumi89 Fishlore VIP Member

    I agree, holy cow! However I politely disagree about platies in a 10 gallon. I had three during quarantining and I wouldn't do it permanently. Three may be acceptable but I think four or five may be pushing it. You have to remember that they are pretty heavy waste producers. :) Just my two cents.
     
  4. aylad Well Known Member Member

    I've seen similar comments from other members. I really have never had a bad experience maintaining 4-5 in a 10gal, but I'll edit that note to reflect different viewpoints. :)

    Thanks for the compliments, too!
     

  5. Daniostetras Member Member

    This is great and really helpful. Thanks!
     
  6. Aquarist Fishlore Legend Member

  7. Ziabis Well Known Member Member


  8. coacoa8506 Member Member

    Wonderful post!!
     
  9. Angel3 Member Member

    Thank you for your help and information!
     
  10. Pandher Member Member

    Thanks! That was awesome and so helpful!