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FAQs on the Swordtail Identification

Related Articles: Swordtails & Poeciliids: Guppies, Platies, Swordtails, Mollies by Neale Monks, Livebearing Fishes by Bob Fenner,

Related FAQs: Swordtails 1, Swordtails 2, Swordtail Behavior, Swordtail Compatibility, Swordtail Selection, Swordtail Systems, Swordtail Feeding, Swordtail Disease, Swordtail Reproduction, Livebearers, Guppies, Platies, Mollies,

unknown fish 11/29/09
Hi not to long ago I had purchased a fish from PetCo and I can't tell what it is I know that the males have pointed lower fins and the females have fan like lower fins but I got this one thinking that is was a male platy to go with my female platy at home. But I have been thinking that it might be a female swordtail any help would be great thanks!
<Hi Miranda. It's certainly a Xiphophorus of some sort, probably a Swordtail, but without seeing the anal fin more clearly, I can't sex it for you. Just for the record, on females the anal fin is triangular, while on males it is bent into a tube-like projection called a gonopodium. Some male Xiphophorus do not fully develop this trait until they're quite old, giving rise to the myth that Xiphophorus can change sex. They can't; or rather, there's no scientific evidence that they can. Cheers, Neale.>

Re: unknown fish 11/29/09
Thanks I was thinking that it might be a swordtail. Do any of these photos help you determine the sex of the fish?
<It's a male.>
Also I have two 10 gallon freshwater aquariums and a 5 gallon. I have mollies, platies, guppies and now that you have told me a swordtail there in the two 10 gallon aquariums. And there babies are in the 5. I really like breeding and caring for fish so I am going to get a 55 gallon freshwater aquarium. I'm going to put mollies, platies, guppies and swordtails in it. Is there any fish that get along with those fish and that breed easily. Thanks a lot!
<I'd just keep these together. All of these fish tolerate slightly salty water well, and Mollies in particular tend to do badly in completely freshwater conditions. So if you find your Mollies plagued with problems like the Shimmies or Finrot, upping the salinity to about 5-6 grammes/litre marine salt mix, your livebearers will do extremely well. Mollies need quite warm water, whereas Platies and Swords prefer things like a little cool, so in a perfect world you wouldn't mix them. Aim for 25 C, and keep oxygenation good. Cheers, Neale.>

Re: unknown fish. Swordtail, sexing... Gonopodium vs. D's "party animal" 12/1/09
Thank you! How is the fish a male swordtail if it has no sword?
<By the shape of the anal fin. Grab the nearest biology textbook, and look up the differences between primary and secondary sexual characteristics. All will become clear! Cheers, Neale.>

Perplexing Platy Species 9/25/09
I was looking up species of platy fish the other night and ran into a perplexing puzzle.
I know Xiphophorus is the class platys, variegated platys, swordtails, and hybrids of the three are placed under.
<Indeed. In fact the Swordtails and Platies sold in pet stores are probably all hybrids of one sort or another. To get pure-bred species of either Platy, Variatus Platy, or Swordtail you need get wild-caught fish or fish bred by dedicated hobbyists.>
Yet I ran into terms such as sp, sp., and 35RD which I did not understand.
<The word "sp." simply means "species", and is how scientists describe a specimen that they cannot, for whatever reason, identify to species level.
In some case the animal concerned does indeed belong to a recognised species, but the scientist just wasn't able to make that identification, lacking the tools, skills or materials. If you found a baby fish in a canal somewhere in Mexico, and you recognised it was some sort of Xiphophorus, but it was too young to identify to species level, you'd call it "Xiphophorus sp.". In other situations, you might find a whole bunch of Xiphophorus you weren't able to identify, and though you couldn't name the species, you could tell that there was more than one species there. In this case, you'd call them "Xiphophorus spp.", meaning Xiphophorus species plural. In other instances, the "sp." or "spp." refers to the fact that these are new species, but you haven't formally identified them. While hobbyists might assume it's quite easy to name a new animal should you discover one, it's actually quite hard work. You have to carefully check the animal hasn't been discovered before, in particular taking care that the thing was reported decades ago and subsequently forgotten about because the description was published in an obscure or foreign language journal. You have to make sure you new animal isn't just an odd version of a familiar species; for example genetic mutations and physical damage can cause animals to look different to other members of their species. And
you'd be surprised how often male and female animals of the same species accidentally got described as different species! The whole process often takes years.>
One species that was listed was listed as Xiphophorus sp 35RD. Now here is where things really got confusing for me. What species of platy is Xiphophorus sp 35RD?
<It's a species of Xiphophorus known to be distinct, but as yet, not formally identified. Because the tropical fish trade often handles newly discovered fish soon after discovery, such fish appear in the shops before scientists give them formal names. So fish exporters give these fish temporary names, in this case, Xiphophorus sp. 35RD. I have no idea what the "35RD" stands for, but it's probably a collecting site or some such.>
Where was it found?
<Mexico, I'd imagine.>
Is it simply an outdated name of another platy, or is this its actual species name?
<It's a "placeholder name" until the fish gets a proper scientific name.
It's analogous to the L-number system used for catfish, where for example the species traded as L001 eventually became Pterygoplichthys joselimaianus.>
What does sp. and sp mean? I know sp. and sp can refer to a species name sometimes. But it does not say when sp or sp. is listed what species to which it is referring. Is it the southern platy, the swordtail, the variegated platy?
<None of the above.>
It simply does not say. And sp and sp. can also mean other things as well.
And what in the world does 35RD mean? Xiphophorus sp 35RD has a taxonomic number, but that is all the information I was able to get. Other than it is a member of the Xiphophorus family.
<Xiphophorus is a genus, not a family. The family is Poeciliidae. In any case, all Xiphophorus are very similar in terms of requirements: relatively cool water, around 22-24 C, hard, basic water chemistry. They're all herbivores, so an algae-based flake food is required. Some come from fast flowing waters (Swordtails) but most come from still water habitats; looking at the body shape is a clue here. If they're streamlined, they like fast water, if they're dumpy, like a Platy, slow-flowing water is better.>
If you have any more information on this species, or better yet a picture, please let me know.
<Not aware that Xiphophorus sp. 35RD is traded yet; certainly never seen a picture. But I can be fairly sure it's small, green, with an upturned mouth and a modest degree of sexual dimorphism -- like all the other (wild-type) members of its genus. Cheers, Neale.>

Mollies and Platies and Swords, Oh My! - 04/20/2006 Hello WWM Crew, <Hi, Chad!> I've just spent much time scrolling through your pages on mollies, platies, and guppies. Found lots of useful info on breeding, feeding, treating, what do to with fry, and sexing... but can't find - maybe I missed it - an answer to my question. Is there a way to tell a molly from a platy from a female swordtail? <Sure.... though differences may seem subtle until you've seen many of all.> I have a Mickey and a twin-bar, both platies as I believe they're the only ones colored this way. <Can find some Mickey mouse swords, now, too.> A few days ago I bought an all-white one and an all-red one. They were labeled mollies at the pet store, but who knows if they even know. They are all getting along and all look similar, if you ask me, except maybe for the fact that the new ones are slimmer, especially the red one, but it's smaller altogether. I've seen pictures online of all-red platies, mollies, and swordtails. Haven't seen an all-white platy yet. <Hmm, where to start, and how not to make it more confusing.... Platies and swords have been heavily hybridized with one another over the years; you will be very hard-pressed to find a platy that hasn't been crossed with a sword or vice verse somewhere down the line. Some platies even develop small "swords" on their tails. Mollies aren't hybridized with either of these, and are usually very easy to tell apart. They'll have sort of.... well, a different body shape.... kinda tough to describe. I would recommend that you go to a few different fish stores and look long and hard at some of each of these types of fishes; you'll develop an eye for it in no time.> Thanks for your time. <Glad to be of service.> -Chad Soucie <All the best to you, -Sabrina>

Swordtails - 11/04/2005 First of all I would like to thank you for all the information that you have provided. <And thank you for the thanks!> My first question is, how can you tell what kind of swordtail? <Umm, as in, what species? Or what "color"? There are a number of different species.... Xiphophorus helleri is the one most common in the hobby, and is available in many different colors.> And does it matter for mating purposes? <Mm, most/all the species can hybridize (though I don't recommend it), but of X. helleri, breeding different color fish is no problem at all.> I have a male that has a green line on his side that extends into the sword on his tail. He has been in my tank for 3 weeks now. The 2 females I purchased at the same time have both died. One died within a week (about 3 days), which the store replaced free of charge, a week later the replacement died. 2 weeks after the original purchase the second original female died. I have a 10 gallon tank, which I cycled using ammonia, my ammonia and nitrite levels are 0. I have to purchase a nitrate test kit, but am assuming that the levels cannot be too high, as my male and about 15 babies (which I presume are from the longer lived original female) and my flying fox are all fine. Two days ago I purchased 2 new females (my male was looking very glum and not eating, he had been alone for 4 days). One of those died overnight, and I have my free replacement. I have a completely orange female and a white female with black fins (this is the replacement and she is missing a huge piece of her tail fin, like something took a bite from her). <Again, color is irrelevant; they will likely breed. I would be concerned about the damage on the tail of the new female, however.> My second question is: Is it normal to lose so many fish? <Normal? No. I would urge you to have caution in selecting new or replacement fish; please read here for more about health in fish: http://www.wetwebmedia.com/FWSubWebIndex/fwdis3setsfactors.htm. Selecting healthy fish to begin with is of great importance.> I always hear people say they know nothing about fish, and their tank has been going for 4 years! I just seem to kill them off. <There are always reasons.... the initial health of the fish you select, the "health" of your system (water quality, etc.).... Fish, like other organisms, don't "just die".... It's all a matter of isolating the cause and fixing it. In your case, as I said, I suspect the initial health of these fish was questionable to begin with. You might want to consider getting/using a quarantine system for new livestock.> I live in the country, about half an hour from the pet store, and wonder if it is too much stress for them. <Mm, no.... Fish can and do go several hours bagged at times.... keeping the amount of time from the store to home at a minimum is a good idea, though, and never leave them in a car where they might heat or chill.... basically, do your errands first, go to the fish store as the last stop on the way home - you should be fine.> My third question is: When I got the replacement for the first female that died, the male showed absolutely no interest in her, even though the other female was obviously pregnant (she had the black spot, which disappeared after the babies appeared). Could the male have exhausted that second female, because he sensed that the replacement female was not well? She never did much and her dorsal fin was always clamped close to her back. <Again.... I really suspect poor health in these fish to begin with.> My fourth question: When should I give up, <?? Only you can decide this.> what if my females die again? <Find out why. Select only the most active, healthy fish you can find. Never purchase fish from a tank with others that are obviously ill.> How long do I persevere? <Uhh, again, the ball's in your court on this.> I reason that if the babies are surviving and growing that my water must be OK, so the problem is the fish. <I agree, to an extent.> One final note, the lady at Wal-mart... <Oh. Uh. Not to be disparaging of any store or enterprise, but I, personally, would not purchase fish from a department store.... find a fish store that is dedicated mostly or only to fish; you wouldn't buy bread from an oil refinery, would you?> ...recommended that I use QuICK cure to treat all the fish when I added these new females, just in case the other females were sick. <I would not. Medicating without knowing specifically what, if anything, you're treating is one of the many routes to disaster....> I have done that 1 day now. The instructions do not say how long to use it, what do you recommend? <I would stop using this now, unless you really have reason to believe these fish have a communicable parasite.> Sorry this is so long. <No worries.> I am grateful for any help, this is my second attempt at a fish tank. The initial attempt was with goldfish, I managed to kill 8 goldfish and 1 pleco that time! <Goldfish are much more demanding of space than most folks realize.... Much is archived on our site, in articles and FAQs, about proper care of goldfish - do please take a look if you're interested.> I was completely unaware of test kits and cycling, etc. So I was somewhat shocked when I started killing fish again after all my attempts to do things properly this time! <Begin reading, learning about fish health. You'll do fine, no worries.> Thank you, -Olivia <Wishing you well, -Sabrina>

Swordtails With Strange Color 1/7/06 Hello, I have looked through your index, but could not find anything that described what I am seeing with the male swordtail that I have. He is a yellow/gold color with a beautiful red and black tail. As he has grown I noticed a sort of light color mottling on his back. (Imagine camouflage fabric) Now he is developing a brown spot on his head. Is this normal skin color changes for a swordtail? I also have 3 female Bettas in the tank with him and I know that they change colors as they age. Thanks for your assistance. --Sue < The swordtail has many color variations that may change as the fish grows. If there are no other signs of illness then I would assume it is a color change and not a disease.-Chuck>

Two Questions. Swordtail ID, Repro. 1/10/06 Hello I sent an email to you guys the other day, but I think my picture was to big. So I decided to try with a smaller pic. If I need to resize it again please let me know. Hope I didn't cause any problems. I bought this fish about a month ago from a pet store. They told me it was a female Sailfin Molly. <Mmm, looks like a female "green/wild-type" swordtail to me (Xiphophorus hellerii) http://fishbase.sinica.edu.tw/Summary/speciesSummary.php?ID=3231&genusname=Xiphophorus&speciesname=hellerii> She is about three inches long, and as you can see not very colorful, but that is o.k. She looks like a large Green Swordtail, to me. Do you guys know what species she might be? <Oh yes> I also have another question, if that is alright. She looks like she is gravid, but has looked like that since the day I got her. Which as I stated earlier, was a month ago. I have been told that the eggs may not have been fertilized, that she reabsorbed them. If this is true wouldn't she have gotten thinner and the gravid spot gone away? <Yes, likely> <Welcome. Bob Fenner>

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