Guppies are probably one of the most commonly kept tropical fish, relatively easy to keep and prolific breeders - there are 1000s of pages on the internet devoted to them. After a decline in the UK the showing of guppies has again become popular and the British Livebearer Association(BLA) have formed a guppy section to harness this interest and currently host an annual "International" Show.
What is a show guppy? normally a fish which has been selectively bred over generations to conform to the ideal standard looked for in shows(IKGH Rules(normally in UK and Europe) and IFGA standards (in US and other parts of the world)(There are other standards!)). A quick look at the BLA and IFGA web sites will furnish you with photos of fish and copies of the judging standards. It is a good idea to type "guppy" into your search engine to find the type and colour of guppy that appeals to you - you will notice BLA/IFGA photos appearing in EBay ads(some edited with photoshop) - does the seller really have fish of that stamp or does he have a cheap pet shop import that vaguely looks like it? Another breeder who's guppy photos frequently appear on EBay is "Gernot Kaden"(use your search engine).
Display(Pet) guppies are relatively cheap normally around the £1.00 mark at Pet Shops(My local pet shop offers 6 for £5.00). These fish have normally been mass produced in the Far East and are imported by the thousands each week into the UK and make great cheap colourful additions to the community tank. Though these fish are colourful and vaguely look like show guppies(chances are their ancestors were show fish) they normally have some defect which negates their use as breeders of a show guppy without a lot of work, tank space and time being put in to correct faults(A challenge for those that want it!). For example dorsal is stubby(common fault cobras/variagated) or dorsal not the same colour as tail( common in half black varieties), bodies elongated and thin(most imports!), tail misshaped(rounded off triangle)/undersized(again most imports). Even if you find what you regard as being a perfect male(meeting show standard) you could have difficulty matching it with a female from the same strain - if you are unable too you are playing russian roulette with genetics and what the offspring will turn out like would be pure guesswork. A pure show strain/line can be expected to be 70%+ true and even the fry of these need careful selection. The breeders of farmed fish put a lot of time, effort and money into producing good quality pet shop fish and rely on repeat orders for their living - as a result the shrewd ones ensure that males and females of their strains do not go to the same importer, some even ensure that they dont go to the same country!!!!
Show guppies are because of the work put into them are more expensive and the more sought after strains command good prices. (2006 1st Int BLA Guppy Show: Blue Moscows £21.00, 2007 2nd Int BLA Guppy Show: Botttom Swords £110.00, 2008 top price £35.00). That said a lot of good quality show fish go for close to the opening bid of £3.00 - £5.00 - depends what is fashionable. Fancyguppies.co.uk currently has a link to a video of the 2007 show and includes footage of class winners.
A lot of UK fanciers have obtained quality stock from US and European Showmen/Breeders and to offset some of the costs of importing these and to spread the gene pool have started to sell offspring on EBay which is an excellent opportunity for the remainder of us to get good fish the like of which we only see at shows or in a book - if you are thinking of bidding, and paying good money for these, be sure to confirm with the seller the source of his fish before placing a bid, you may even be directed to the "originators" web site". It has not taken long for "show", "US", German" or "Italian" to be common terms when selling guppies - generates a better selling price - OK if it can be verified and photos of the fish or their parents are included in the auction.
Unless it is display guppies for the community tank you are after beware of photos on EBay showing a tankful of fish which only vaguely bare a resemblence to each other or where the male and female are clearly of different colours. If you crossed a daschund with a great dane you would not expect 50% daschund and 50% great dane puppies - what you would get is 100% mongrel - guppies are no different!!!!! Buying guppies off EBay as opposed to from the local pet shop is a considered purchase because of the additional postal charges incurred - make sure you are getting something that will give pleasure for years - not a year by which time a mixed population will start to revert to wild type ancestor.
There are loads of good books on guppies but some of the the modern ones(after 1990 - most of which I have) tend to have tie ins with fish farms and the guppies shown are not in my opinion "show guppies(rounded off deltal tails being the most common fault)" but there is loads of good information within and they are still worth the purchase price and a read (I think Stan Shubels "Aquarium Care of Fancy Guppies" is a good modern one - and no I dont sell them!! - I got my copy off EBay)).
Aquabid has good pictures of show guppies(US stock) but it is a case of look but dont touch as it would be illegal to import them without an import licence.
Guppies being fast growers and such prolific breeders - regular batches of young every month - you can afford to be selective when choosing your strain - one pair could be the ancesters of 100s two years down the road!!! It pays to ensure that the original pair are top quality and worth the trouble of rearing their young. If you want to raise quality youngsters for sale here on EBay purchase quality stock, give the fry space, keep at 78f, carry out regular 10% water changes and feed frequently(all they will eat within 10 minutes). Feed live or frozen baby brine shrimp, microworm, and a variety of crushed flake (some of it should contain vegetable/spirulina to prevent internal damage - guppies are omnivores).
Guppies like any other fish are occasionally hit by disease - a good tip to keep these to a minimum and cut medicinal costs is to run a UV filter which kills all free floating pathogens, spores, bacteria and algae - a good cheap one is the Fish R Fun variant(again I dont sell them but they are readily available on EBay). These wont cure a disease already in a fish's body but will by killing the free floating stage cut the transmission from fish to fish. UV filters are invaluable when raising fry or when new fish are introduced to an established tank.
If you are experiencing problems with your guppies fancyguppies.co.uk is a good place to look for solutions and even has a forum should the problem not be covered in their articles.
There will be a major charity fish auction taking place in Redditch UK where numerous hard to find tropical fish will be on offer(guppies, endlers, killifish, betta(all types), wild catfish, cichlids to name but a few). Details can be found by pressing yellow charity button on TA Aquaculture site.
The 5th UK BLA International Guppy Show will be held in Nottingham in Autumn 2011 - fancyguppies.co.uk will again be the place to go for full details nearer the time.