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FAQs on the Swordtail Behavior

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 Compatibility, Swordtail Selection, Swordtail Systems, Swordtail Feeding, Swordtail Disease, Swordtail Reproduction, Livebearers, Guppies, Platies, Mollies,

Is there other cause for male swordtail to scratch besides ick?        4/14/15
Hi guys, I'm at a loss here. I have a 55 gall tank with a male African cichlid electric blue, with a male red swordtail platy, and a large Pleco.
The cichlid is 17+ years old so he doesn't harass the male. I've been treating the tank for 5 days now for ick, because my swordtail was scratching on the blue cup. I'm using jungle ick guard, 3 doses of salt with the water changes, and heat treatment. The 3rd day I raised it to 85, on the days before it was in the 80s. Today and yesterday the temp has been
at 86, and the fish seem okay, but the swordtail has still been itching.
I haven't seen any spots on any of them, nor do I see anything else external.
The nitrates in the tank has been really high lately, I adopted the tank from my mom, who stopped cleaning it, with only the cichlid in it. I just got the nitrates down to about 5 or 10, after months of work. Could the water change be making him itchy? I've been using tetra easy balance plus with conditioner.
Any advice would help and be greatly thanked!
<Short answer is that fish will "flash" or scratch against solid objects anytime they feel their skin or gills getting irritated. So while Whitespot and Velvet are two common reasons (Velvet in particular often affects the gills long before you see it on the body) they're not the only ones. Sudden changes in pH in either direction, non-zero ammonia and nitrite levels, and high levels of silt in the water column are all other possibilities.
Certain medications can irritate their gills as well. Do bear in mind Swordtails are fairly specific in their requirements. They need hard water and relatively low temperatures (22-25 C/72-77 F) as befits stream-dwelling fish from upland parts of Mexico. Review, and act accordingly. Cheers, 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.>

Swordtail Behavior/fighting....   10/14/11
I have a 10 gallon tank with:
<This aquarium is much, MUCH too small for these fish.>
4 female swordtails (All different kinds)
2 male swordtails (1 mery-gold, one Red Velvet)
1 Female Dalmatian balloon molly
1 Female butterfly balloon molly.
<Mollies do require somewhat different conditions to Swordtails, so this combination isn't ideal. Do read:
The fish are picking on each other and I am wondering if I should allow it, or, because of Petco's return policy, I am still able to return some of the fish. Here is the situation.
The Red Male Swordtail is picking on the other only male Swordtail (the mery-gold one). The Red one is cornering the Mery-Gold one. The Mery-gold will sit on the bottom slightly curled up and shake a little bit. The Red one will go next to him, lean towards him, and show off himself. He will then either chase him or bite him until the marigold one finds a place where he can get away from him. There are lots of hiding places in the tank. There is a large piece wood with holes and hiding places, and there also several live plants.
<Male Swordtails are extremely aggressive. In tanks smaller than 30 gallons, it's unwise to keep anything other than a single male, a group of females, or a male alongside two or more females.>
ON TOP of that one male, red swordtail picking on him, the female Dalmatian molly picks on him!!
<The female Molly may well be "grazing" rather than being aggressive. Do bear in mind that Mollies are most herbivores, and they do need a good supply of green foods to stay healthy. If they feel hungry, they may well nibble on the mucous on other fish.>
I have a 5 gallon tank, but I don't want to put the swordtail in there because I think that is too small for them. (I have the other 5 gallon with some guppy fry in a breeder net). I had put the marigold swordtail with one of the female swordtails in the 5 gallon because I thought the male swordtail was going to die, because he was hiding in some of the plants, absolutely still. When I put those two in there, they acted totally normal.
They even breed a couple times, and ate normal as well. I put them all back in the 10 gallon though because a 5 gallon with a breeder net is just too small for them. I don't know what to do!
<Do read.>
ALSO, in their own battle, the Dalmatian Molly that picks on the Marigold Swordtail, also picks on the butterfly molly!
Everyone eats normal except the male marigold molly who is bullied constantly. He just hides in a corner or in the plants, or stays on the bottom a lot....
I am not sure what to do! I can still return the following to the store because of their return policy (it's been less than 30 days):
The 2 female mollies
The Red Male.
My other option is waiting on a larger tank. When I go back home next (I am away from home at school), my brother in law is going to give me a 29 Gallon tank :)
So, I honestly have no clue what to do...
Please if you could give me some advice, that would be awesome!
Thanks so much in advance.
<Do read, understand what these fish need, in terms of social behaviour and space. Cheers, Neale.>

Disappearing swordtail, beh.  04/22/10
I've been searching for answers and haven't been able to find any that really answered my concern. I have a 36 gallon tank, I've just got it for a little over a month now, I have 7 guppies, 2 bottom feeders,
<Corydoras catfish? These need to be in groups of 5 or more since they're social and gregarious. In smaller groups they will be nervous and more likely to become stressed.>
1 algae eater,
<Which is...? Ancistrus, the Bristlenose catfish is fine. But either Gyrinocheilus aymonieri or Pterygoplichthys pardalis would be too large for a tank this size, reaching some 30-40 cm within a year or two.
Gyrinocheilus is also incredibly aggressive once more than half grown. Do read about fish before buying them.>
and two swordtails, one female and one male.
<Keep two or more females per male, or the female will be harassed.>
I have in the tank 2 live plants and two figures in it also. Me and my kids enjoy watching them swim around and feeding them, but just this past week my swordtails has developed "Ick" and I've been trying to treat them.
But my female has been disappearing!
<Likely harassed by the male.>
No one goes into the tank but me, and no one sees where she goes....usually if they hide in the plants we see them, the figures have plenty of spaces in between to still be able to see them anywhere, and we can still locate all the other fishes but her! But early in the morning she does reappear, but then by late afternoon, she disappear again! Where can they hide???
<She's clearly good at hiding. Quite normal when people keep these fish badly. The females are harassed by the males pretty much all the time.>
I also have white sand on the bottom...
<Which fish hate, and you will find their colours all washed out.>
can she and is she under the sand???
<Not likely. But note this species "jumps" and is good at escaping from tanks.>
This has been going on for a few days now, is it from the "Ick" or normal behavior???
<No not normal. Cheers, Neale.>

green swordtail... beh. mostly    7/31/09
Hi my swordtail is supposed to give birth soon. She has been acting really funny today. She has been nipping at all my fish.
<Swordtails can be fairly aggressive; they're not the best community fish out there.>
I have 2 black swordtails and I just got a platy yesterday. Is she moody because she's going to give birth soon?
<Hard to say. Gestation is typically 4-6 weeks, depending on temperature.>
What are the signs besides the dark spot that she is going to give birth?
<The "dark spot" is no sign at all; in fact many Swordtails and Platies have this dark patch even when they're not pregnant, and males can have them too! It's important to remember that the "gravid spot" applies to Guppies and other very small livebearers, because they have a thin enough wall of muscles around the body for the expanding uterus to be seen. Bigger fish, like Swordtails, have too much muscle for that to be the case, at least, not reliably.>
Also I have 2 floating plants and gravel on the ground. Is that enough for my baby fish to hide in?
<Soon find out.>
I don't have a filter or heater. All I have is bubbles. It is a ten gallon aquarium.
<Too small for Swordtails; they're stream-dwelling fish, and like to swim about. Look at their shape! Water temperature needs to be somewhat warm, not quite so warm as many other tropical fish, but still above room temperature; 24 C/75 F is ideal. If the water is too cold, and the water isn't filtered, they will, eventually, die. No question about that. Do see here:
I read that I'm not supposed to put water in the aquarium from a nother aquarium but I forgot and put in my platies fish water from the pet store.
Will they be all right?
<No. For a start, you never put water from the bag the fish came home in into your aquarium. The best approach is this: empty the fish bag (and the fish) into a bucket. Over the next 30 minutes, add a cup or so of water from your aquarium every 5-10 minutes into the bucket. When you're done, use a net to life the fish from the bucket and put it in your aquarium. This is a variation on what's called the "drip method" and avoids mixing water from the pet stores with your aquarium. This minimises exposure of your fish to parasites, and also avoids putting ammonia from the fish bag into your aquarium.>
My Black fish gave birth the day I got her. I think it was to soon but I'm not sure. The fry died that day. Can swordtails give birth to deformed fish?
<Does happen, but usually if the fry die, it's because there's something
very wrong with the aquarium.>
What kinds of fish besides swordtails and platies can they breed with?
<All Xiphophorus species will hybridise with one another.>
What do swordtails and platies require.
<See here:
How do you know if your platy is male or female?
<Males have a modified anal fin that looks like a slightly crooked finger; it's the gonopodium and used to inseminate females. This will be apparent on fish over 3 months in age.>
I would like to know everything there is about breeding swordtails and the signs of there going to give birth, how they should act, how they act when there sick, how to take care of the fry, everything.
<Read, my friend. "Everything" covers a lot of ground!>
Thank you for reading this.
<Cheers, Neale.>

Green swordtail pooping constantly  3/18/09
I recently purchased a female green swordtail, we also have 3 other female swords in the tank. The green one is obviously pregnant huge black gravid spot though not very round, but all she does is poop. All the poo seems to be 2to3 times the length of her body and she just keeps swimming along with it hanging out. I was just wondering if something could be wrong with her or is just pregnancy. We feed her Tetra tropical food flakes twice a day.
<Greetings. The issue here sounds like constipation. Swordtails (and indeed Xiphophorus species generally) are herbivores, and expect a diet rich in green foods. Algae-based flake foods should be the staple, not standard tropical fish food, which is formulated for carnivorous fish such as tetras. Supplement the diet with cooked or tinned peas, cooked spinach, Sushi Nori and other soft, green foods. Leave algae to grow in the tank! Epsom salt at 1 to 3 teaspoons per 5 US gallons could be added if the fish seems bloated; otherwise, just stop using flake food (including algae-based flake food) and stick with the peas, Sushi Nori and other fibre-rich foods.
Certain live foods have a laxative effect, notably daphnia and brine shrimp, so those could be used too. Do also remember to optimise conditions: Swordtails need hard, alkaline water that isn't too warm; for 10+ degrees dH, pH 7.5-8, and a temperature no higher than 24 degrees C (75 F). Exercise is important to these fish, since they're stream-dwellers rather than pond fish; make sure the tank is roomy (at least 60 cm long) and equipped with a strong filter. Cheers, Neale.>

Xiphophorus (vanishing colours?)   10/17/08 Hello Crew! I have two platies.. One of them seems to be getting lighter in color. At first, it was light yellow, but it is getting white everyday? Any theories as to why? Thank you! Marion <Need more data... Is the skin on this fish getting cloudy, as if its mucous layer was getting thicker? That's a symptom of a variety of different problems, not least of which is poor water conditions. But if the fish is otherwise normal but simply losing its colour, then that's more likely harmless, if not particularly welcome. Some commercially bred fish are "juiced" in various ways to make them more colourful than they really are. As time passes, they revert to their proper colours. Because Platies are herbivores, they will have their best colours if given a diet rich in plant matter. Spirulina flake food is widely sold and ideal. So also are algae wafers sold for Plecs. Pop half a wafer in, and let them peck away at it all day. Augment the diet with crustaceans such as brine shrimps and live daphnia. Between them, these foods will provide the carotenes and other chemicals Platies need for their best colours. Cheers, Neale.>

Xiphophorus; behaviour, repro    8/3/08 hello again, sorry to bother you Neale, <Hello,> I swear that sending emails to you will not become a common practice of mine- I can assure you this. And I hope you don't think I'm a nuisance already (for, this would be my third question to you). <Fire away!> My platys are not sick, their tank's ph, ammonia, chlorine, etc- they're all fine. Nothing is physically wrong with my fish. My problem is simply this: I bought some new fish (I've upgraded to a 20 gallon- so don't worry I have the room). One of my new fish is a white Mickey mouse platy and he seems fine and mild tempered; he displays no aggression towards any of my fish, except one. She is a female I've had for a long time and I've grown quite fond of her. <The males will pester whatever female they deem to be "fittest" in terms of being the most attractive recipient of their genetic material. How they make those choices is complex. But in any event, what you're seeing simply means he likes this girl the most.> I'd hate to have anything happen to her. It pains me to see the new fish chase only that one female fish around. Other female fish are fine and so is my one other male. My question to you is: why is the new white male singling out only one of my fish? <Entire PhD theses are written on mate selection! Broadly speaking, male livebearers are shorter lived than the females. They are smaller, brighter colours, and often encumbered with things that make them worse swimmers (e.g., longer fins). So males have to breed quickly. Females are bigger, camouflaged, and stronger swimmers, so they can take their time and choose mates carefully. Producing sperm is cheap and easy, so males can afford to mate frequently. Females are stuck with the eggs their born with, and each pregnancy places a heavy energy demand on the female, so she wants to mate only when it is in her best interests to do so. This creates a tension between the males (who want to mate urgently) and females (who want to mate carefully). Bottom line: males will pester whichever females they want to mate with. This is why with livebearers I like to tell people to be generous about the size of the tank; to keep them in fairly big numbers to dilute aggression/harassment; to keep more females than males; and to provide lots of floating plants so that females have hiding places.> I've never seen this before. Usually when I pick a mean fish, it will attack all the fish in the tank, or at least two or three. This one is dead set on following and sometimes nipping at just one fish in particular. <Does happen.> Will this behavior go away with time? <No guarantees.> Should I give this situation time? <Up to a point, but if she's having trouble resting and feeding, then that's going to cause problems ere too long.> Will the stress of constantly being chased back and forth kill one of my favorite fish? <Conceivably.> I am very worried. I would like to keep the new fish, as he is very pretty and I want to keep a good female to male ratio so that my one dominant female doesn't become too possessive of my one male. But I understand that if the new fish's behavior is not something that will go away, I will have to return him to the store. <If you have space, I'd add some more females. I can't remember how big your tank is, so be sensible about this. But adding females usually benefits the livebearer aquarium. Adding decent sized floating plants (e.g. Indian Fern) would be another cheap-and-cheerful solution that might work.> Thank you for taking the time to read my questions and I hope I'm not a nuisance. The questions on your site don't really seem to be geared toward platy behavior so much as platy illnesses. I figured a direct question to you would be a better avenue. <Indeed.> Thank you so much! <Cheers, Neale.>

Re: Xiphophorus; behaviour, repro  8/4/08 Neale, Thank you for responding to my questions. I had a feeling it was something to do with fish affection but I wasn't sure. Better to be safe than sorry, right? <You mean fish aggression rather than affection, I suspect! And yes, better safe than sorry.> I do have room for three more fish and this time I'll be more careful as to what sex of fish I choose. My tank probably does need more hideaways and I'll work on that as well. Again, thank you for all your help! <Sounds like a good plan. Good luck! Neale.>

Male Swordtail Terror  6/26/08 Hello Neale and all WWM Crew. Happy Summer to you. <And to you> This is a question on a male swordtail terrorizing the other two in a 125 gallon tank. The end string below summarizes our fish quantity, but recap is 50 fish; community of platys, swords, mollis, Corys. There are 7-8 assorted female swords. There are 3 males; a medium pineapple, a small black (mature, and a large red 'standard LFS' male. All have been in the tank 6 months to a year. The tank has corner pumps, many fake rocks, plastic grass, etc to hide in. Early on the very large red male was boss and would harass the black one only, who has never attained great size. This stopped. All was calm. Now the very large red is no longer the kingpin male. Though not the largest, the pineapple has begun to really harass, chase, and bite the black and the red. <Strange> Both are becoming skinny, show fin loss, and hide in corners. They can't get to food without being chased the length of the tank. They are not diseased in any way. With 7 females, we thought we were ok; decided to let nature take its course over the last two weeks. But we couldn't stand it, the pineapple is downright being a brute. Today we isolated the pineapple in a large plastic colander in the 125 tank. <Good move> Here are what we feel are our options: 1. Buy more females and hope for the best in the 125 tank. 2. Move the pineapple to a 10 gallon empty fry tank that is operating, along with two females. Hope he wears himself out and the other two recover and fatten up in the 125 tank. 3. Move the red and black male swords to the fry tank along with 4 females to fatten up. 4. Do nothing and hope for the best. (We feel the two harassed swords will die of starvation if we do this.) 5. Hang the pineapple from a yardarm in front of the other fish as a lesson at high noon. <Heeee! Hang 'em high!> Please tell what you think and elaborate as to the +/- of each option. Many thanks, Rosemary and Don <I would go with #1... and possibly try changing the food. Do look into supplanting what you use with Spectrum pellets... sometimes nutritional deficiency can be a large player in affecting fish behavior. I have found this food to be excellent nutritionally, very palatable (to the fishes!), and a calming influence. Cheers, Bob Fenner>

Re: Male Swordtail Terror/Food, Ratio Males to Females  6/27/08 Mr. Fenner, <Rose and Don> Many thanks for your helpful reply. Our pineapple sword remains in solitary on bread and water pending purchase of more female swords. <Good> Missed asking the question of what ratio of males to females might solve our problem. If 2.33 to 1 is not working (7 Females and 3 males), how many females total would be appropriate for 3 male swordtails in our 125 gallon tank with the current animosity? <"The more the merrier"... at least three to one... Am now humming a modified Beach Boys tune...> We feed twice daily. Always daily Wardly Algae Tablets (Corys and the rubber lips), and alternate Tetra Tropical Flakes with shrimp pellets or blood worms. We never personally thought much of the shrimp pellets, too messy. How does that sound for balance and nutrition? <I'd add some more with greens, or greens themselves...> Anything there a waste of time? We will immediately add in the Spectrum Community Pellets to the mix when we get to the LFS> <Is a great product... as you and your aquatic charges will find> Thanks again and cheers, Rosemary and Don <And to you, BobF>

Swordtail Fry Growth 11/2/07 Hey WWM, My swordtail gave birth about a month ago and I was wondering if this is about the proper size for them. The picture is attached. <Oh yes, very nice. Thanks for sharing. James (Salty Dog)>

Re: Fin rot - water changes | summer heat | Melafix and Furan, now Xiphophorus beh.  07/24/07 Bob-- <Anna> One more question ;--). this time more about fish's behavior. <Ok> I noticed that most of my fish (actually all, with the exception of a female red sword) "look at me" by using a left eye. No matter which side of the aquarium I choose for an observation, the fish I monitor always positions itself such a way that it can examine me by using its left eye. I do not know why my fish do it ;--) but I find it somehow funny. <I too... as in unusual> Another remark relates to my red sword. Few months ago that fish got sick and I had to separate it and place it in the hospital tank. I am not sure if fish can "go through depression, <I am very sure that many do experience such states> " but when that red sword was in the hospital tank it looked miserable ;--( I was checking on the water condition every day, but the water was perfect. Also, the hospital tank had lots of hiding spots and artificial plants, yet the fish remained in the same corner all the time. I even cut a fine strip of a colored film and enveloped it around the tank to provide maximum "privacy." Yet still, the fish stayed at the same corner... Also, after a medication got completely dissolved and the fresh water was added to the hospital tank the fish still looked quite "sad." Finally, after 2 weeks of treatment I moved that fish back to the display tank. Within just a few days the red sword completely rejuvenated... I know the red swords are "community fish," but is it possible that fish can find a companion of other fish so indispensable ...? <Yes> Anyway, the more I observe my fish the more I am convinced they are truly amazing species. <We are in agreement> Anna the aquatic follower ;--) <And leader. BobF>

Swordtail fish, beh.    7/19/07 Hi, my name is Mélida. I just started my first 10 gallon tank. This morning I was cleaning the tank, and when I went to put my fish back in the thank the net was broken so I grab each one with my hands, but when I put the swordtail male in, he looks like and S. Is he going to die? Or his going to get better? I feel so guilty of his condition and I dont Know what to do. Sorry about my spelling. Im from Panamá I dont know how to write in English. <Hello Mélida! When fish are alarmed they automatically bend into an S shape, and then open up again rapidly. It's called the "Mauthner Reflex" and allows them to quickly swim away from danger without "thinking" about it. It is similar to our reflex, when we pull our hand from something hot or painful. Anyway, if the S shape doesn't change, and the fish stays bent, this is more serious. It can be caused by physical damage. Fish are very "soft" and easily damaged. If your net is broken, then use a glass jar or something similar instead (in fact a glass jar is better for spiny fishes like catfish). Sometimes a fish will go into strange body positions when it is severely stressed. It may recover if left alone. So at the moment, wait and see what happens. Cheers, Neale>

Re: Swordtail fish   7/19/07 Hi Neale . Thanks for your help. My swordtail fish is doing great I'm so happy that his ok. And this morning I found a bunch of fries in the tank. (45). Gracias for your help and god bless you <Thanks for the kind wishes, and likewise, I wish you and your new baby fishes good luck! Neale>

Hello! I have a few questions about swordtails! Beh., comp., repro.  07/01/07 Dear Crew at WetWebMedia Hello, my name is Oksana. I have two swordtails, a male and female, and a 1 1/2 gallon tank. (Yes, I know, terrible, but my parents won't let me get a bigger one.) Bob, the male, has been living a few months in my possession, seems very healthy. Betty, (The female, I just got her today, June 30) seems healthy too. Before Betty, we've had male swordtails, and Bob, being the dominant one, has always shown a little aggression toward the smaller and weaker ones, and unfortunately, they perished. So anyway, Bob was left alone. The problem is, is that Betty is pregnant. We got her pregnant already from the fish store, and Bob keeps nipping at her. Not full class "bites" just nips. She chases him away of course, but I keep wondering if that's normal swordtail behavior. I have read most of your pages in breeding swordtails, but do you have any extra advice? The local petshop has already to take in the young fry when they're a few months old, but I have a question on that too. How fast do fry mature? I have seaweed in my tank, a filter, and a hiding place, (Yes, I wonder how they all fit and the fish still have swimming room...) so I don't think I need to take the female out when she gives birth. Any other tips on what to do will be fully appreciated. Thanks very much, Oksana <Greetings. Yes, 1.5 gallons is far too small for swordtails. A 20 gallon tank would be my recommendation for fishes as large and active as these. Males are aggressive, and in small tanks it is safest to keep just one male plus 2-3 females. Females do get harassed by males. There's nothing you can do to prevent this in a tank as small as yours. In a bigger tank, you can rely on plants and rocks to give the female security. But in a small tank, she has nowhere to hide. Long term, the male will likely kill any fry that appear as well. Do not, under any circumstances, place the female in a breeding trap or breeding net. Swordtails are too big for these, and get stressed. Worse case, they die, but more usually spend all their time thrashing about trying to escape. As you know, swordtails are very fast and extremely good at jumping. The ideal when breeding livebearers is to place the female into another tank where she can deliver her fry safely. Good luck! Neale>

Baby Livebearer Changing Color  04/29/07 Hello WWM, I have a very peculiar problem. I have a tank with a couple of fish - a guppy, an orange swordtail and a black molly, with two of the surviving babies of the swordtail and the molly. One of the babies is orange, and the other is orange with big black patches on its tail. They are about two weeks old, and a little less than 2cm long. Now, I noticed that sometimes the black patches on the tail of the mulatto baby fade until they are almost gone, and the orange gets almost transparent! Then when I come back and look at them again, say, 10min later, the black is back and the orange is rich and bright again. The other baby is smaller and not very intensely orange yet as it is, so I can't tell if there's a difference, and the adult fish seem to be okay. I think the guppy fades too, but maybe I'm just paranoid. This has happened twice now, once just after I turned their light on in the morning (black was faded, but came back after light was on for a couple minutes), and the second time I can't remember, I think again after turning the light on. It doesn't happen every time I turn the light on after a night of darkness, just occasionally lately. Is this normal? Are they just trying to hide in the dark? I'm confused. They seem very happy otherwise; I haven't had any other problems. Please help. Thanks, Didi < The color changes are the result of mood swings. A confident little fish will be showing off. A shy, timid fish that is afraid it will be eaten, will try and blend into its surroundings by dulling its coloration.-Chuck.

Swordtail With Fading Spot 04/30/07 Hi again, Thanks for the response. I don't think that's the problem though. Of the two babies, the one with the fading color is the dominant one. It's about twice the size of the other one, even though they are of the same littler, and always eats with the big fish, as opposed to the little one which swims around the bottom and eats falling food bits. The small one hides more, too, while the big one swims around wherever it wants to. I didn't think mood mattered, so I didn't mention these details in my first email. So, assuming the fading baby is not shy and it's not mood swings, is there anything else that could be going on? Thanks, Didi <Still think its mood and here is why. The dominant baby is only dominant to the other, smaller fry. Not to the other adults. So in order to mingle with the adults it shows its submissive dull colors. If it showed its dominant coloration it would be chased by the other adults.-Chuck.>

Re: Swordtail Baby Changes Markings When The light Is On   5/2/07 But... but... but it changes back to intense colors when I turn the light on too feed them, a.k.a. the time when it mingles with the adults the most, to get food! When it's eating alongside them by the surface, its colors are bright. Dark black. Always. And it swims nosily around the big fish like that, unlike the smaller one which stays away. The only thing I can link discoloration to, from my observation, is lack of light in the tank. Maybe it loses color when it sleeps at night and is more vulnerable, to blend in? Sorry for emailing you again... :-D Didi < There are definitely color changes when the lighting is changed. Many fish communicate using their markings and colors. When it is dark, most fish try to blend in to their natural surroundings so not to attract a predator they cannot see. When the light is on and they feel safe, they will show off to the other fish. Your swordtail may be a male and be thinking about spawning or at least attracting a female. This may account for some of your observations. It doesn't sound like any disease problems.-Chuck>

Swordtail problem   1/11/07 Hi,    <Hello>   Y'day I got about 8 mollies and a couple of swordtail. When I introduced them to our tank they took sometime to settle down. But the female swordtail kept running up and down the walls of the tank. But this morning when I checked on them the female swordtail it seems to stay on the surface minimal movement. Sometimes it goes to the bottom of the tank but still stays with minimal activity. Is it some kind of a disease? I have no idea what could be the problem Please help.       Thanks      Veronica. <Likely just "settling in", acclimating to the move, new system... Please read here: http://wetwebmedia.com/FWSubWebIndex/swordsysfaqs.htm and the linked files above. Bob Fenner>

When do male Swordtails develop their swords?   12/4/06 Hi. I have a Swordfish "101" question. <Okey-doke.> When do male swordtail fry finally develop their sword? <Generally around the same time they develop their gonopodium, or male sexual organ, which happens around 4-6 months.>   I have 10 swordtail fry which are 3 months old and none have yet to develop swords. <I have not personally bred swordtails, but with my molly and platy fry, I've noticed that sometime around 4-6 months they seem to have a "growth spurt", and develop their distinguishing sexual characteristics, adult coloration, and size...>    If it helps, the swords are either called Wag Tail or Tuxedo but they're definitely not of the completely orange variety. <It can be hard to tell ultimate coloration on juvies.  I've thought molly fry were going to be completely white, only to find out they are really Dalmatian spotted when they become 4 or 5 months old!> On another note, I'd like to thank you for stressing, on the WWW site, the use of proper English grammar.  I imagine it's a terrible waste of your time having to correct the errors of so many people that write-in... <write in, no hyphen!> ...who are either too lazy or too ignorant to write properly. We need the WWW crew in our schools! <Thanks for the kind words.  Honestly, I personally don't mind a few mistakes here and there (heck, we all make them), but the "e-slang" that so many folks insist upon drives me nuts.  But then again, I am a member of the apostrophe Protection Society, and as such, in all likelihood, not completely normal...> Thank you very much for your time. Ricky V. <You're welcome.  Enjoy your swordtail fry - livebearer juvies are so cute and fun, in my opinion! Best regards, Jorie>

Swordtails ... dis.? Beh.    11/28/06 Hi, I love your site. Anyways I got some swordtails from my LFS and I got 2 males and 3 females. Anyways they seem to have been settling in good, (for the past 3 hours I've had them) and I've noticed that one of the females is just sitting by the bottom. It is mostly black so I cannot tell if it is pregnant by looking for the fry's eyes. Are there any other signs? <See WWM re> Its fins towards its head (kind of look like arms) are moving pretty fast. Another question, all of my swordtails are staying towards the bottom of the tank, <This from likely just being new... recovering from transport, new surroundings... acclimation> I have a Gourami that likes to stay near the top, could it be the Gourami pushing them down? <Possibly, but doubtful> Also I have 2  yo-yo loaches patrolling the bottom, could those get aggressive towards the swordtails too? <Good question/s... but not likely here either> Thanks in advance, Tommy <Welcome. Bob Fenner>

Swordtail & Corydoras behavior  - 05/13/2006 Hello again, All my swords are now active and schooling. I've figured out the problem with the last female I bought. While at the pet store the other day I noticed they had a new tank marked "high finned platy". Apparently they had the red swag high finned platys and red swag swords in together, <Yikes... not smart. Can/do inter-breed> on top of that this platy is a male because he has the single pectoral fin. <Mmm, not this> My criteria for determining whether I was buying male or female swords didn't work on a platy :P I'm going to get a couple female high finned platys so hopefully the male sword will stop picking on the male platy. <A good plan> Looking at him you'd never know he wasn't a sword (other than the large top fin), he even schools with the swords but the male chases him around every once in a while and at feeding the male sword gets very aggressive toward the platy. <Yes, natural> Anyway, enough of my rambling, I've got another question for you. I originally bought 3 Corys, 1 bronze and 2 albino, I thought because they were the same species they would school. <Maybe> Well one albino died the first night, and the remaining albino and bronze would just sit by themselves all the time in the corner or under a rock. I waited a couple days to make sure no other fish were having problems in the tank and added 2 more bronze and all 3 schooled up right away but the albino still just sat there, he'd come out to eat and then go right back to his hiding spot. I had already setup a larger tank for my Betta and decided I'd do a school of albino Corys in it so I bought 2 and moved the one from my other tank to the new one, and again, he found a hiding spot and just sits there, the other 2 schooled right up. I added 3 more a couple days ago and all 5 school and ferret around the bottom looking for food but the original one just sits there. <Give it time...> If another Cory or I bother him he'll get up and start looking for food for a few sec.s and then he swims back to his spot. He'll also swim out to eat when I drop shrimp or algae pellets in. I guess I'm trying to figure out why he won't school or at least do something besides just sit there. Thanks in advance. <Takes some individuals a bit of time... Patience here. Bob Fenner> Swordtail behavior  - 04/27/06 Hello, while looking up some odd behavior I observed today I came across your site and only one question was left unanswered. Being my first freshwater aquarium I bought a book at PetSmart and it suggested the sword tail as a good starter species to cycle the tank <Uh, no...> so I bought 3 as it suggested and put them in, 2 females red (with black fins) and a male pineapple. The larger female stays hidden almost all the time staring at her reflection and occasionally tapping the glass. The smaller female and the male seem to have paired up and swim around together a lot and sometimes just go chill by the larger female in her hiding spot but there's no aggression between them. The guide I'm following though is for a 29 gallon tank and I have a 37 so I decided to add a couple fish to the plan and went and bought another pineapple female the next day. After putting the pineapple female in tank she began swimming all over but the small red female seems to be chasing and nipping at the pineapple female and sometimes the male will join the small red female in a charge but never really chases the pineapple female like the small red female does. The small red female and the pineapple female are about the same size. Should I separate them or is this just a normal adjustment period of the fish establishing their hierarchy? <It might be that the "new-ness" of the tank, changing/evolving water quality is a contributor here, but Swords are naturally somewhat nippy... I would leave all as is here, and keep monitoring your system for cycling... adding no more livestock, carefully feeding till it is done completely. Bob Fenner> Swordtails What does it mean when a male nibbles at the female swordtails ventral area?<could be a mating ritual or just aggression...I would keep an eye on the two and see if the female is getting hurt or stressed out. If the latter occurs I would put the female in a breeding net> Is he trying 2 kill her unborn babies in an attempt 2 mate w/ her?!! <doubtful-but would keep a close eye on the fish, IanB>

Swordtail Strangeness Last Friday, I bought 3 female swordtails. I'm not positive what variety they are; two are sort of goldish colored and the other is orange with black fins that are tipped in yellow (really pretty!). Well, in the LFS, the orange one had some black spots on his head. I asked the girl working if those were normal and she said yes. I honestly didn't have a clue so I just trusted her. It was the only female of the variety left so I didn't have much choice. Well, I got home and quarantined all three in the same tank (10 gallon, Whisper filter, 78 degrees F, 50% water from main tank, 50% treated tap water). Several hours later when I checked to see how they were doing, the black spots were gone! So what does this mean? Is she sick? Was she sick? Should I quarantine them longer than I'm planning (1 more week)? Ever heard of anything like this? All three of them seem very healthy right now and those spots have never come back. Thanks for any help you can provide. David <<David, I have no clue. The only thing I can think of is a color change due to stress, so the black spots could return. Although platies rarely change color due to stress, but I guess it's possible. I can't think of any other reason for the spots to disappear so quickly. Quarantine them for a couple of weeks. At any rate, keep an eye on your fish for any other physical changes, and test your water regularly for ammonia, nitrite, and nitrates. Good luck! -Gwen>>

Aggressive female swordtail 5/31/04 I have a couple of swordtails, (1 male and 1 female). The female (who is larger a bit than the mail) is really aggressive. they were ok the first couple of day after I got them, but now the male is always hiding, and every time he goes out the female attacks him so he goes back to hiding. what does that mean?? <either the honeymoon is over, or the beer has run out <G>. But seriously, it sounds like a simple case of territorial aggression. If the tank is not overstocked, do consider adding more leafy coverage/plants (plastic or live), or perhaps rearranging what you have if plentiful already. Best of luck, Anthony>

Strange Swordtail Behavior -Old or Sick? Hi there, Sorry to bother you but I am hoping you can help.  We have a mixed 15gal tank including some swordtails tetras and two clown loaches.  Recently the oldest of the swordtail females - (we have had her over a year and she is at least three inches long & full grown when we got her) - She has started acting very strangely and stopped eating. All the other fish in the tank look fine and eat and swim normally.  This one swims "frantically" around near the surface of the water with the top of her head just barely brushing the surface. I have not seen her eat anything for at least a week.  She has gotten very thin, but continues to swim despite apparent exhaustion which occasionally has her drift to the bottom for a "rest" period. She then returns to the surface and sticks her nose toward the air again.   We have both an internal Eheim filter (we live in the Netherlands so you may not know these brands) as well as some extra aeration via a bubble wand since the internal filter doesn't aerate. We have done two 25%-30% water changes in the last two weeks in case it was a water quality issue.  We have also tried treating with a locally available "broad spectrum" product "Exit" that claimed (in Dutch) to cure "most common fish ailments.   So if this is not simply old age. apparently it is an Uncommon ailment. I would like to know if this sounds like anything remotely curable. She just keeps getting skinnier and skinnier and she was so strong to last this long, but she is simply getting worse not better, but doesn't seem to want to die of old age....Any ideas? Thanks for any input! Laura < It sounds like an internal bacterial infection that may have been drought on by advanced age. In a clean warm quarantine tank I would try Metronidazole or a heavy dose of Furanace. You fish has been ill/weak for a while so it may not be strong enough for a triple dose of Furanace. So try a single dose and see if there is any effect.-Chuck>

Shy Swordtail Hello! I'm new to the fish game, learning all the time - thanks in large part to your site! My question is about a female swordtail I bought a couple weeks ago. I think she's pregnant, buy my question is about how she's acting - she hides all the time! I have a large piece of coral in my tank - she spends about 80% of her time squeezed into the nooks and crannies. The few times that I've coaxed her out (at one point, I thought she might have died in the coral), she leaves the coral and goes straight into another decor item I have, and hides there! I have one other female swordtail, a male, plus several goldfish and 6 neon tetras. All the fish get along really well, except for this one shy one. Is this behavior an indication that she's pregnant? Or, is this just the way she is? Any suggestions for helping her "come out of her shell? Thanks for your help! Tom <Many females will go off by themselves when ready to drop. Both she and the fry would make an easy target for a hungry cichlid if not. Could just be a shy fish also. The more places a shy fish as to hide, the more it will come out. It will feel safer. The big problem I see is mixing tropicals and goldfish. Not good. The Neons and swords want a temp in the high 70s to low 80s. The goldfish at least ten degrees cooler. They also do better on different diets. For the long term health of these fish I suggest you return the goldfish. To keep several goldfish for life requires a tank of over 150 gallons. Don> 

Swordtails Dueling it Out Hi there, here is the history--We bought 4 swordtails 2 males and 2 females, the one female died within 2 weeks, now the other female is pregnant. My 2 males seem to be getting really aggressive with one another, and I am wondering what we should do. Is this normal??? We don't have the set up to breed right now so we are not worried about keeping the fry but I also don't want the males to kill each other off??? Any suggestions??? < When it comes to mating games survival goes to the fittest. If the males are not breeding then they are attempting to drive off potential suitors. I would add lots of plants and give the loses many places to hide and /or rest. You could always separate them if you had another tank.-Chuck>

Aggressive swordtails 8/9/05 Hey I have a 15 gallon with 3 "teenager" marble sailfin mollies, and 6 swordtails (2 red-white, 2 green, 1 black, 1 pineapple). I have 3 males and 3 females, and I know that the female ratio needs to be higher, so I put 1 male in my 10 gallon, but my males continued to be very aggressive. <Happens... ratios are better at three or more females per male> The mollies seem to have nothing to do with the swords, and the swords are not aggressive toward the mollies. <About right> So I continued to watch them and the "bully" male is quite larger than the other 2 males, and 2 females. He chases around the two males and the two smaller females. However, the large female chases him around!! So is there anything you suggest before I can find some time to find some new healthy females to add?? Thanks. BMERANG <Separate the bully... in a hanging net, breeding trap, floating colander in the tank. Bob Fenner>  

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