Keeping and Breeding Platies (Xiphophorus sp.)

Keeping and Breeding Platies (Xiphophorus sp.)

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Platies are colourful, peaceful, hardy and do not require a lot of tank space. As a result they are amongst the fish most commonly kept in home aquaria. They are also a fish recommended to new hobbyists as they breed easily and do not require particular care, other than observing the basics of aquarium hygiene.

 
 
 

One of the ancestors of the fish currently available in the hobby, Xiphophorus variatus, has a variable colour pattern which explains its name (variatus); it is believed that the various colour forms currently available in the hobby have originated from this fish.  The fish currently available in LFSs are selectively bred aquarium strains, usually imported from the fish farms of South East Asia. These fish have mixed lineage including ancestors from Xiphophours hellerii, Xiphophorus variatus and Xiphophorus maculatus. They are available in various sizes and colours; most of these varieties have commercial names to enhance their market value (such as Mickey mouse platy, marigold, sunset etc). Purer and rarer forms of platies are available through particular breeding programmes.

 
 
 

Platies are generally small fish reaching a TL of 7 cm, though occasionally larger individuals have been reported. They are quite peaceful fish and get on with a number of small fish such as neon tetra, corydoras, Loricariidae etc. They are often used as "dither" fish in tanks hosting catfish. They swim at the top of the water column; in the wild they feed on plants, insects, small crustaceans and worms. The reported life expectancy of the fish in a home tank is 3-5 years, though, again, there have been reports about individuals who lived longer than that.

 
 
 

In home aquaria platies interbreed readily. We have kept various colonies from time to time, mainly as dither fish for tanks with colonies of young catfish growing up. The fish have done pretty well when cohabiting with colonies of larger, more aggressive catfish too. It goes without saying that as this fish is part of the natural diet of predator cichlids tank sharing with such fish should be avoided, except, that is, if a hobbyist intends to keep their cichlids on a live food diet.

 
 
 

It is often argued that platies breed readily when they are placed in slightly salty or brackish water. This is not quite the case. Platies need medium hard water to thrive so it is advisable to add minerals to very soft water.

 
 
 

Our preferred setup for a platy tank is pretty simple. We use small squarish or oblong tanks (40 - 60 lit), serviced by an air filter. If an internal pump is used we make sure the flow is really low (the fish do well in higher current once they get used to it however such current adversely affects the plants). We add an air stone, also on low and a heater set to 25o-26oC.The temperature is dictated by the needs of the tank mates of platies; the platies themselves do well in lower temperatures too. The substrate is sand (aquarium or collected from a beach). We use good lighting (1 W per lit of water) to ensure the growth of plants such as Riccia fluitans, Ceratofyllum demersum or Vesicularia dubyana (Java moss); these plants are essential to protect the young fish, just after they are born, from the adults. For purely decorative purposes we occasionally add to some tanks Anubia barteri, Anubia nana or Microsorum pteropus (Java fern). Tank furniture include pieces of bogwood and mopani wood, arranged in arching shapes or forming little caves. This allows females and young males to hide or avoid persistant or aggressive adult males. As the water in Manchester is pretty soft, we add bicarbonate of soda to stabilise the pH to 7.6 and freshwater minerals to raise the hardness to 9-10 dgH.  The Ceratofyllum gets thinned out regularly, to ensure young fish are not caught in it; should that happen the young fish will suffocate.

 
   
 

We feed the fish fresh vegetables (spinach, blanched lettuce leaves, wild rocket etc) and a good quality staple diet. Once or twice a week we also offer frozen bloodworm, mosquito larvae, artemia salina or cyclops. The frozen food is more of a treat; the fish do perfectly well without it. The mouth of the platies is has an upward tilt; fishkeepers take this to indicate they should only feed their platies flakes or other floating food as the fish will not be able to feed from the middle or the bottom of the water column. This is very much not the case. 

 
         
 

It is important to ensure that there are considerably more females than males in the colony; we would suggest a ratio 3-5 females to a male. This will ensure that the females will not get stressed by the male who will be constantly chasing them to spawn. The males are easily distinguished from the females. Swordtails have an elongated ray at the lower end of their caudal fin (sword); all male platies are smaller and less plump than the females and have a gonopodium at the ventral area. They use this to fertilise the females.

 
   
 

Female platies can store unencapsulated sperm aggregates, called spermatozeugmata; these are used to fertilize eggs for a long time after spawning. As a result females are able to release up to six broods following a single mating.  Removing the males from the tank for a period of time is a strategy used by a number of hobbyists to ensure birth control.

 
 
 

We occasionally use this strategy to obtain broods from particular parents; it is interesting to see the various colour  which is an indication of the mixed genetic heritage of the parents. To ensure that the selected male  will be the father of the brood we place our female in a tank of her own - or with other females - until she releases all the fertilised broods she is carrying. We then put the  chosen male in her tank and allow nature to take its course. The male and female below produced a brood with various colour fry, of which the young male showing in the third photo was the most attractive:

 
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Platies are live bearers;  after a gestation period of four to seven weeks the females will release the young. The number of the newborns will vary but usually one should expect 20-50 fry. The fry are transparent and tiny and will hide amongst the ceratofullum or the Java moss. Without a hiding place, fry will become prey to the adults.

 
    
 

Gravid females are easily distinguished by their bulging mid-body area. The area grows considerably prior to the female releasing the brood. As it grows it acquires a lighter colouration, which is the result of the skin around the area being stretched. This is sometimes referred to as 'developing a lighter spot' and is an indication that the fry are about to be released.

 
 
 

It is usually advised to place a gravid female in a breeding trap prior to her releasing the fry; this ensures all the fry will be caught and raised in safety. We have never done this; we feel that available breeding traps are too small for our pretty largish females and the experience will stress them out at a time when they can least cope with it. If the tank is stocked and decorated appropriately females will always find a quiet place to hide and release their young, usually amongst the ceratofyllum leaves. When stressed or otherwise in poor condition, females have been known to abort.

 
 
 

Most hobbyists will provide special food for the young, including crushed pellets or flakes and artemia cysts. We never found this necessary. Our fry graze on the ceratofyllum and the java moss; in any case a lot of food usually collects there which the fry are able to eat. It is important to regulate the food in the tank when fry are present. The young fish are tiny and it is quite easy to literally "throw the babies out with the tank water" so water changes should be performed carefully and kept at a minimum. We always use a pre-filter to cover the end of the pipe which goes in the aquarium. As an added precaution we syphon the water into a bucket and check it carefully prior to discarding it. Over the years this has proved a real life saver.

 
       
 

Young platies grow quite quickly; at 4 weeks they are visible in the tank without particular effort and at 2 months of age they measure roughly about 2 cm TL. At 6-7 months they are sexually mature.  To ensure that vital space for new births is always available it is important to thin out the colony quite regularly; we re-home young fish when they are about 2-3 months old. Hobbyists who are interested in fixing colour traits may wish to keep fish with unusual colours or patterns and put them in a separate tank to breed.

 
    
 

A lot of hobbyists prefer to acquire Xiphophorus hellerii type males as their appearance is considered more attractive. These fish are subsequently placed in tanks with various females, where they spawn. In cases like this it is worth remembering that the presence of a fully grown adult male Xiphophorus hellerii in a tank will spur the females while it will inhibit the growth of other, younger males. The later should therefore be removed and placed in a tank of their own in order to grow up properly.  It is also worth noting that lab experiments indicate that females prefer males with longer swords; should a hobbyist wish to breed a male with a short sword they should make sure this male is either the only male in the tank or that males with longer swords are removed to another tank. (1)

 
      
 

Platies produce a considerable amount of waste for a small fish; syphoning the substrate is a good way of avoiding rapid deterioration of the water and diseases.

Photos by the authors.

 

Notes / References

(1) A. Meyer,  W. Salzburger, M. Schartl†, "Hybrid origin of a swordtail species (Teleostei: Xiphophorus clemenciae) driven by sexual selection", Molecular Ecology, Volume 15, Issue 3, Pages 721 - 730, © 2009 Blackwell Publishing Ltd


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