Please visit our Sponsors
FAQs on the Swordtail Systems

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

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

Swordtails are BIG, ACTIVE fish that need a "long" 20 gallon tank, minimum. In small tanks they tend to jump out, become aggressive, eat their babies, and frankly don't do well. NM

Swordtail fish       1/16/15
Hiya, I've got a 23L tank that I've had for 12months with two danios, platy, and my male swordtail fish..
<23 litres? Much too small for this Swordtail/this group of fishes.>
The last few days I've noticed that the back end of the swordtail fish has started turning like a brown colour but its not on its sword though just the back bit before its tail... It still seems fine eating swimming...
<Incipient Finrot would be my first suspicion without seeing a photo. 23 Litres is so small, and Swordtails are so big and active, that sooner or later this fish damage itself and/or get stressed by the poor environment.
Review, and act accordingly. A bigger tank, suitable filtration would probably fix things without the need for medication.>
Sent from my iPhone Jay
<Sent from a computer. Neale.>

Swordtail fish..sys.         1/21/15
Hiya thanks for getting back to me... I didn't know it was a swordtail till about 6months to having it it just turned one morning...all my other fish are fine and i always make sure its clean...
<Glad to hear it. Nonetheless, Swordtails need something upwards of 100 litres/26 US gallons, since their adult size is considerable, over 8 cm/3 inches. Their streamlined shape is meant for dashing about in quite fast flowing streams, much like minnows. Lots of folks get small tanks, buy a bunch of fish, and everything seems fine for a while... a few weeks, months. But the reality is that you can't buck science with wishful thinking. As fish grow, they demand more oxygen and produce more waste.
Conditions in the tank deteriorate. Fish get stressed, the more sensitive species first. Stress leads to weakness and disease, and eventually fish die. Dollars to donuts, the population of an overstocked tank will (quite literally) die back to the level the tank supports. Stocking 20-30 litre (5-8 US gal.) aquaria is an art. It's doable, but difficult. Shrimps, Ricefish, Heterandria formosa, Ember Tetras, the smaller Badis and Dario species perhaps... these are the kinds of things to think about.
Alternatively a Betta, even Dwarf African Frogs. But Swordtails... nope. Poor choice; won't live for long, at least not healthily or happily.
Cheers, Neale.>

Re Swordtail; sys.       1/21/15
Hiya.. I asked at pets home whats the best set up and that's what they said get so i just took there advice...
<Pets at Home honestly let themselves down on the fish front. Some stores aren't bad, and I've met employees there who really do know there stuff, but most people working at Pets at Home have no idea at all about fishkeeping beyond the very basics. This is a common problem with the "big box" pet stores that do fish as a sideline. The Fluval Edge 23 litre (6 US
gallon) aquarium is one of their more popular items
, but it's almost too small for fishkeeping. A while back I wrote an article for Tropical Fish Finder about stocking this tank:

That gives you some ideas about stocking these tanks, but in all honesty, they're not the best tanks for beginners. Expert fishkeepers can come up with some really nice projects based around them. A coldwater tank stocked with Java Moss and Heterandria formosa (Dwarf Mosquitofish) would be terrific fun for example. Colourful shrimps are another project, with
numerous kinds available if you know where to find them. But pretty much ANY common community fish will be too big for the smaller Fluval Edge, and even its bigger brother, the 46 litre (12 US gallon) version, is only suited for the smallest community fish (Neons, Endler's, and so on).>
I've not had s problem yet with any fish its just the colouring on my swordtail... Have you any ideas as what it good be please... Thanks
<Hope this helps. Neale.>

Swordtail Questions. sys., beh., hlth.   12/10/11
<Hello Craig,>
About a year ago I bought a pair of red swordtails from a local pet store. A year later I have 5 swordtails 3 female and 2 male.  They grew up in my 25 gallon tank along with a Pleco
<This will need a huge aquarium within 1-2 years, 55 gallons upwards.
Unless you're keeping a Bristlenose Plec, Ancistrus sp., which would be fine. The Common Plec sold in American aquarium shops is Pterygoplichthys sp., which gets to 45 cm/18 inches within 1-2 years. It's a giant of a fish, and despite its reputation, creates more problems than it solves.>
and 2 zebra diamos. 
<Now, do understand that Swordtails aren't sociable. There is certainly no such thing as a pair, and while females may get along, males are very intolerant of one another. Swordtails are fish for big tanks. Look at their shape -- they're streamlined and built for speed! Keep them in a small aquarium and they'll be frustrated and unable to get out of one another's space. Net result, aggression.>
Of course the females will be pregnant.  I bought a 10 gallon tank to transfer the females into once they start getting closer.  The 10 gallon is perfectly set up been up and running with a few more zebras in it and another baby Pleco.
<May be a well set-up tank, but 10 gallons is too small for Zebra Danios to be honest, let alone Swordtails. All you're doing is creating problems.>
My question is:  2 of my females seem to be hanging in a corner of the tank where it is more dimly lit with one male (the bigger one) just kind of hanging around and 'lightly' harassing them.
<What happens with these fish. See above.>
Should I transfer them now?
<Again? To which tank? You need 30+ gallons for Swordtails, end of story.
If your tank isn't a good 90 cm/3 ft long, it isn't big enough for these quite big and obviously streamlined and fast-moving fish.>
I look for the large belly and gravid spot but I'm really not sure what I'm looking at.
<There's no reliable "gravid spot" on Swordtails. Remember, the gravid spot isn't a magical patch of colour that appears to say a female livebearer is pregnant. All it is is the uterus pushing against the muscle and skin around the back end of the abdomen. On very small species like Guppies, the dark uterus can be seen as a dark patch because the muscle and skin are quite thin. But the bigger the fish, the more skin and muscle, and the less clear the uterus becomes. On Swordtails and Mollies, it's usually not clear at all. Instead, you can safely assume any female kept with a male will be pregnant, and batches of fry will normally be about 4-6 weeks apart. Since Swordtails are cool climate tropical fish, you should be keeping them at between 22-24 C/72-75 F, which means they produce young slightly more slowly than high-end tropicals like Guppies.>
I was wondering if this behavior is normal.
The 'runt' male and female still are going about their normal business. 
However when I study the fish closer looking for signs I noticed that there is a whitish coloring around the gills converging under the chin of all of the swordtails.
<Hmm, doesn't sound good.>
Is this normal?
I read stuff on gill flukes and keeping clean water, which I make a 25% water change weekly.  Could this be normal swordtail coloring?
Or do I have to take drastic measures? 
<Depends. Could be mucous from irritation of the gills (e.g., but Whitespot or Velvet); could be dead skin or mucous from physical damage; could be a bacterial infection like Mycobacteria that is unfortunately very common among livebearers when they aren't kept properly (and, to be honest, hardly rare among cheap farmed livebearers either).>
pH is 6.8-7.0,
<You water is clearly much too soft. You need to be adding about 0.5-1 tablespoon of Epsom salt per 5 US gallons, and 0.5-1 teaspoon of sodium bicarbonate (baking soda) per 5 US gallons. Note that I have not said anything about adding generic aquarium salt -- ordinary salt does not raise hardness.>
Ammonia is  >.25ppm,
<Much too high, and likely close to the problem here. The only safe level of ammonia is zero. Anything above that, and you're doing something wrong, and your fish are at risk.>
Nitrite is 0 ppm, and Nitrate is around 2-3 ppm.
<These both sound find. That your ammonia is high suggests your filter isn't adequate to the task, or you're overfeeding, or, possibly, there's chloramine in the tap water you're using. Make sure you use a water conditioner that removes chlorine, chloramine, ammonia (tap water, not from the fish!), and copper.>
<You're welcome. Cheers, Neale.>

swordtails & fries 06/02/09
I have some swordtails the red/orange like color and a neon sword and Mickey mouse platies. In a 10 gal tank
<Far too small for either of these species; a "long" 20 gallon is the minimum for Platies, and Swordtails really need to be kept in a 30 gallon tank. Just look how streamlined Swordtails are! Those are fish built for
swimming! What could be crueler than keeping "greyhounds" like them in a pokey 10 gallon tank?>
I want some general info on them like what the ph should be
<Both these Xiphophorus species need hard, alkaline water; aim for hardness 10 to 25 degrees dH, and a pH around 7.5 to 8. Neither wants salt.>
and the water temp
<Fairly cool, around 23-24 C being idea. The water needs a moderate current for Platies, and ideally a strong current for the Swordtails.>
care of and the breeding and any thing you can give me on general info on the fries.
<The plural of "fry" is "fry", by the way. Anyway, all this is on WWM;
start here:
...and then follow the articles and FAQs linked therein.>
thanks Irene
<Cheers, Neale.>

Swordtails, sys., comp.  8/21/08 Hello, I am not new to keeping fish but I have a few questions about the swordtail, the HiFin Lyretail Swordtail in particular. First, I have a 5 gallon Minibow freshwater fish tank, and it has a in tank whisper filter plus a 15 watt light bulb which keeps the tank's Temp. at about 74-78 degrees, I have only one fish in the tank at the moment, it is a half-moon male Betta, and I wanted to get two swordtails, a male and a female, I was told by a good friend who keeps the swordtails that this would be fine as long as I didn't purchase anymore fish after that, is this true? And Is all of this correct Information that i have received? Also, if my male Betta has been living in this tank for a while now, and is healthy and active, couldnt the swordtails have the same luck? Aren't they both hardy fish and aren't they both tropical fish as well? So shouldnt they coexist together and be able to live in about the same water conditions also? Sorry for the questions, I just really need to know this from some one who knows their stuff!! Lastly, If I don't want the swordtails to breed, should I just get two females, or will the male and the female get on with their life and forget about each other? Thank you so much for your time, P.S. I did read about the girl who was keeping the swordtails in a 1.5 gallon fish tank, and I can only fit a 5 gallon fish tank in my apartment so is this okay? Thanks and have a good time, sincerely, Mason. p.s.s I haven't changed my email since I was 16, I am currently 18 so this should explain the kid part of the email address! Talk to You soon! <Hello Mason, this is Merritt here today to answer your questions. Well, first of all a 5 gallon tank is just not big enough for swordtails, sorry but you can still keep other interesting fish in a 5 gallon. Also, just purchasing a male and a female would not be good, due to the male being aggressive to the female, it would be better to have 2 - 3 females per male. Another aspect is no, the male and female would not ignore each other, the male would pester the female to mate and then you would have fry to deal with. If you got females you would have to get more than two so a pecking order could be established. Both swordtails and Bettas are hardy fish and can easily be kept together if the tank space allows. Have a great day! Merritt A.>

Xiphophorus hlth.  1/15/08 Hello, I really need help. <Oh...?> I have two swordtails in a ten gallon tank and I just got them. <Too small! Too small! Swordtails are BIG, ACTIVE fish that need a "long" 20 gallon tank, minimum. In small tanks they tend to jump out, become aggressive, eat their babies, and frankly don't do well.> I just set up a new aquarium and I waited 4 days before putting the swordtails in. <The "waiting" was a nice thought, but didn't do anything. Tanks are cycled only when there's a source of ammonia for the filter bacteria to eat. That can be a few hardy fish, or it can be a few dribbles of ammonia from a bottle. Either way, that's what matures the tank. So adding live fish into an immature tank (what you did here) exposes the fish to ammonia and nitrite while the filter grows into being. The whole process takes about 6 weeks, during which time you need to measure the nitrite levels in the tank, and be prepared to do water changes as often as every day. OTHERWISE, the fish will sicken and die!> At first they were fine. However, on the ninth day, my swordtails started to look very sick. <I bet. How many water changes? How many water quality tests?> They have very cloudy skin and they look like they have "worms" hanging from their body. The "worms" are white as well as some of the skin. <Likely Fungus and/or Finrot. Treat quickly unless you want the fish to die. There are medications that treat both at once, such as Maracyn (in the US) and eSHa 2000 (in Europe). Use them! Don't use herbal stuff like Melafix/Pimafix; they're just not all that effective.> Sorry I don't have a picture, my camera broke. What disease is this? I treated it with Mardel CopperSafe. Here is a picture of it. http://www.virbacpets.com/modules/getimage.php?prodID=190&size=235. <Not what you need here. Coppersafe is for treating Ick/Whitespot.> I have not tried salt yet but I will be doing this soon. <Salt isn't a cure-all, and shouldn't be treated as such, regardless of what the guy in the store says (mostly, he wants to sell you very expensive boxes of what is basically cooking salt).> Is it safe to use this medication with salt? <Possibly, but I wouldn't bother.> I have also raised the temperature up to about 80 degrees. Is there anything I am missing? <Yes: you haven't tested the water quality, have you? I bet you'd find the nitrite levels are VERY HIGH. You have a problem here because the ammonia/nitrite in the water will be killing the fish every bit as effectively as the Finrot/Fungus. So, you need to do three things. First stop feeding the fish. No food. At all. None. Nada. Secondly, do a big water change, 50% at least. Then add the medication as instructed. This may require several doses across 2 days or more. When the course is finished, you do the third thing: 25-50% water changes EVERY DAY until your nitrite test kit registers zero nitrite in the water. When that happens, slap yourself on the back and say well done, because you tank will not be mature. You can then SLOWLY add more fish, one or two every week or so.> Please help. I don't want my two swordtails to die. Thank you bob and crew. <Cheers, Neale.>

Swordtail repro., systems   1/11/07 I have a question about my 55 gallon FW with Live plants tank.  The tank has been cycled over 3 months using BIO-Spira, and currently have 2 Swordtail females, 2 Female Platies/1 male, 5 Corys and a Pleco.  Water is Ammonia-0, Nitrite-0, Nitrate 25-30ppm, <Mmm... do look into keeping NO3 under 20ppm... Read here: http://wetwebmedia.com/FWSubWebIndex/fwnitrates.htm and the linked files above> PH 8.0. <A bit high... could be dangerous in the event of a nitrogenous anomaly> Anyway to make a long story short, I bought the 2 swordtail females with one being very pregnant, and the other not so.  The very pregnant one still looks the same after a little over 3 months, <Mmm, not pregnancy... "just" fat> however, the other is about the same size pregnant now and I found one baby about a week ago, but shouldn't there be more? <Mmm, yes... Xiphophorus give birth over day's time usually, but it may be that either the other young were consumed... or are hiding effectively from you> I'm just wondering if she has some kind of problem with the babies in her, or maybe they aren't developing correctly? <Yes, this is a possibility as well> Anyway I haven't had any losses just wondering if I should try something, as I have a 10g Nursery.  Also two of the Corys are looking pale, and wondering if they like a different PH than 8.0+.   Thanks <Not good to move livebearers when they're close to parturition... and the pH... might be adjusted... via water used/stored for changes... Please read here: http://wetwebmedia.com/FWSubWebIndex/fwph,alk.htm and the linked files above. Bob Fenner>

Swordtail info. Repro., sel., sys.     11/27/06 Hello every one, <Hey FJ! JustinN with you today> I was cruising the net looking for info on the gestation period of Swordtails when I found your site. Wow lots of info. Great site. My hats off. <Thank you, is appreciated> It's been a while since I've had a serious tropical tank. ( I got into freshwater for a long while ) I've recently set up 3 tanks for tropical fish. 1 show tank 55gal. and 2 20gal. 1 for isolation and 1 as a nursery. plus 2 more are on the way. <Sounds well thought out> Although it's been awhile I think some of your readers might like hear a couple of the basic thoughts I have on this subject and maybe they'll have less problems. <Ok, will post for all to see> 1 - Maintain your ph.. @7.0 no more no less I have found this makes for a better well rounded tank with less stress and less stress means happy fish, and happy fish ( from my observations ) means less parasites. 2 - Double the recommended amount of salt in your system.. the fish don't mind but the parasites do. 3 - Never let the water temp drop below 78f  I find 78-->80 degrees is perfect (for happy fish) 4 - Quarantine your plant for awhile just as you would your fish...before putting them into your main show and/or stable tanks. 5 - If possible feed your fish more than once a day. I like to do this when I have breakfast & dinner. Never feed just before you turn off the light. 6 - Frequent water changes pulling 50% of the water out of the system every 3 months and changing you filter carbon and floss every month (and cleaning the filter itself) 7 - Minimal decorative gravel on the bottom of the tank (less the better) 8 - Know before hand how certain fish will interact with others. 9 - Have a diversity of life in the tank, fish ,snails, crayfish, frogs, plants, well you get the idea. <Not too keen on the idea of crayfish with fish here, but I digress> 10 - Last but not least a nursery tank should be jammed with plants and snails. I know this is all stuff you already know but maybe you could put it in your own words and let the people know. My wife thinks I'm crazy ...and she's probably right, but happy fish can make you happy. Thank you for your time. FJ. <Thank you for your suggestions. We will post for all to see/read. -JustinN>

How many in a 30g? I have recently come across a problem with my 30 gal. tank. I have a pair of neon swordtails that gave birth to babies last October. I had a lot of friends want some babies, so I saved them from being eaten by their mother. 7 months later, every single one of my friends is "unable to take them." Now, I've grown too attached to them and don't know what I can do. I want to keep as many as I can. I originally kept 6 of them to be in the main display, so along with the other fish I have, that makes 10 total. What is the maximum I can keep w/o overloading my bio-filter? I have an AquaClear 200 along with a 2 inch substrate of fluorite and a few plants. Weekly water changes of 4 gallons or RO/DI water. Thank you very much. ~Ed <<Dear Ed, you can use a nitrate test kit to determine your stocking capacity. Simply test your 30g on a weekly basis. Let's say you want to aim for 20ppm of nitrates. Let's say you just did a water change, you test the tank, it's 20ppm. You wait one week, and test again. Is the level now at 40ppm or higher? That will mean you need to do weekly 50% water changes to keep the level at 20ppm. If you can't keep the nitrates low, say around 20-30ppm with a weekly water change, then you have too many fish. Simple enough. If the nitrates creep too high, you will find yourself doing larger volume and more frequent water changes. It is basically up to you to decide how often you want to do the tank maintenance. If once a week water changes is okay, then stock the amount of fish that the test kit says to. If you prefer once every three weeks, then cut down on the stocking level until you can let the tank go for three weeks without the nitrates skyrocketing. Make sense? -Gwen>>

How Many in a 30g II Gwen, Thank you very much for your quick reply. Now, assuming that the nitrate levels will remain stable and my biofilter can handle this many fish (right now there are 22 babies with the 4 original fish), what about over-crowding? Is this where the 1 inch of fish/gal comes into play? ~Ed <<Ed, the one inch per gallon is just a generalization we give to people, kinda like the rule for changing your car's oil every 6 months. I personally hate this rule, since it totally depends on how many fish are in what size tank, what species they are, etc. Unfortunately, the one inch per gallon rule is quite easily broken. With goldfish, cichlids, marine fish, for example, you simply cannot use that rule. Goldfish produce too much waste and grow too large, cichlids are territorial, marine fish require excellent water quality and any level of nitrate is too high for them...so basically, the BEST way to tell your stocking level is to test your nitrates on a regular basis. Any other method is simply not going to cut it in the long run. Because your nitrates may NOT remain stable, especially as your fry grow, so testing is the ONLY way to know what the level is and therefore, how often you will need to do a water change. Let's say you do a water change every time your nitrate level hits 40ppm. That could happen after three days, or three weeks...depends on how many fish are in the tank and how fast they are growing. If you are tired of doing water changes every three days, remove some fish! Your biofilter should be able to take care of any reasonable amount of fish, given time. Adding too many large fish at once to a stable system can even cause ammonia spikes, so be careful. -Gwen>> 

Swordtail Disappearing Act? Hi there I am new to this so I was wondering if you can help.  <<Hi, I probably can. Hopefully in time!>> I recently purchased 5 swordtails 3 male 2 female (did not know this till I got home). This morning all was ok, this afternoon one of the males has disappeared without a trace.  <<Very likely driven right up OUT of the tank by one of the other males. Which, by the way, really must be returned for another female, or things could get very ugly for the girls.>> The swords are the biggest fish in the tank are all males are similar in size. Where has he gone and has he been eaten? Jim <<Check around that tank VERY carefully - cannot stress/emphasize how easily fish get into the smallest places. If you find him in time you might be able to revive him. I feel he has MOST CERTAINLY been driven out of the tank. Check even the weird places. If he just died in there you would see the other fishes nibbling on his rotting corpse. Marina>> 

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: