I would say that the most accurate way to tell how pregnant a female guppy is based on the colour of her gravid patch/spot. The gravid patch is a dark area located towards the back of the fishes stomach, as the guppys pregnancy progresses this area will get darker and darker. What makes the gravid patch dark is actually the fry's eyes which are developing in the fishes womb, as the fry develop inside the mother guppy their eye's will get darker and darker and this will show through the thin skin of the mother guppy, creating the gravid patch.
Guppy fry's eyes are usually black, however for example they can also be blue too, this will not create a blue gravid patch though, simply it will appear less dark on the outside. None the less though, i would say the gravid patch is still a very accurate way to see how far along a female guppy is in its pregnancy .
The gravid patch/spot;
The average guppy pregnancy lasts between 3-5weeks depending on various conditions in the tank, the amount of fry she is carrying, and her age/size etc.
Anyhoo, now we has this clear I will begin- I have used a pale yellow bodied female as an example for this thread as in such a female you are most likely to see the changes that the female goes through in her pregnancy- on darker bodied or coloured females things like the changes in the gravid patch may not be so obvious;
The female guppy is not pregnant at all in this picture and there is no sign of a gravid patch. She has probably given birth recently, this is the least pregnant a female guppy can get, she has most likely already mated with a male by this stage though, so will starting to get pregnant again. She may even choose to use the sperm of a male she mated with from a previous mating she had before her last pregnancy (as female guppy's can store sperm in them for up to 6-7 pregnancies maximum). She will be growing new eggs inside her at this stage, however she will be very slim at this stage still.
There is the slightest orangey/pinkish/dark yellowish tinge to the gravid patch area, even though there are no fry in her at the moment, the eggs inside the female guppy are beginning to darken ever so slightly as they grow larger and more in quantity and the first stages of the fry's development start to take place. However, the female guppy is still very slim and is showing no other visable signs of her early pregnancy. If she has no sperm in her to further this stage in the pregnancy, she will just keep on growing eggs in her and the gravid patch will not darken any futher.
The gravid patch area is certainly getting darker at this stage (although it is still pretty pale in colour), there are certain signs that are beginning to take place like this that this guppy is most likely in the early stages pregnancy now, and she is beginning to look a bit plumper around the stomach area.
As the guppy's pregnancy progresses, her gravid patch becomes darker and darker and she looks more and more noticeably plump around the stomach area. It looks like she has a darkening jelly inside her womb.
You will be starting to see the actual fry's eyes through the skin of the pregnant guppy at this stage, although they will still look like little specs surrounded by orangey jelly. The female guppy should only have about a fortnight or less now before she gives birth now.
The female guppy's gravid patch is getting particularly dark by this stage, you can see how tightly packed in the fry are getting as they grow inside their mother! The female guppy is not only getting continuously plumper around the stomach area, but her "chest" is also getting larger too. The female guppy may be showing the first signs of being ready to give birth at this stage i.e. hanging around on her own in a quiet/subdued mood in densely planted area's in the tank. It is not long now before she gives birth, I would say 1 week or less.
This is the last and final stage in the female guppy's pregnancy. Her gravid patch is so dark it is practically all black, and she looks very pregnant/fat indeed. She will be displaying behaviour like she is about to give birth (see stage 6 for example), and will be trying to ignore the male guppy's attentions.
However the male guppy's will probably be giving her a lot of unwanted attention at this stage- chasing or following her around, pecking at her business end and displaying towards her to get her attentions. The main reason why male guppy's pay so much attention to heavily pregnant females like this is that they are;
a. Desperate to get the first mating in once she gives birth, so they are most likely to father her next batch of fry, and
b. So they can eat any fry born immediately, which may belong to another males. By eating their competitors fry, their fry will have more of a chance when they are born etc.
The female guppy could technically give birth to up to 50+ fry, but 20-30 fry is a lot more common. A lot of these fry will be eaten in their first couple of days of life, which is why some people prefer to remove the pregnant female to a separate tank away from the main community.
When female guppy's give birth, they express a hormone which stops their appetite and helps prevent them from eating their own fry, however as far as I know this hormone only lasts for up to 12hours, so the fry are only safe for a little while from their mother (this should still give them plenty of time to swim off and hide somewhere though).
Guppy fry will instinctively hide in planted area's and the such like in the tank, so it is good to provide some heavily planted areas with an array of plants.
I would not advise putting the pregnant female guppy In a breeding net/trap at any point unless she is being severely harassed by male guppy/s or other fish in the tank and needs a break from them. Breeding nets are still stressful things though, so you should aim to have the female in the net for as little time as possible as the stress from being in the breeding net could even cause the female guppy to abort her fry.
"My female gave birth to some eggs!?"
This happens occasionally in guppy keeping and is a major sign that something went wrong in the pregnancy. Guppy fry do not all develop at once at the same rate inside the mother, some will be partly developed while some will still be eggs. When female guppy's abort their fry, you will often see some eggs and partly developed fry, the eggs and partly developed fry will not survive outside the mother.
The reason why the guppy aborted its fry is most likely due to stresses the female was experiencing, these stresses could be numerous things, like over-harassment from the males, general bulling in the tank, sickness/disease, water quality problems, lack of space/over-crowding or overstocking etc etc.
When female guppy's experience such stressful conditions, they will either abort their fry, or re-absorb them back into the womb and turn them back into eggs and start the pregnancy all over again. When female guppy's re-absorb the developing fry or eggs it is their way of ensuring that they only give birth in conditions where the fry are not highly likely to die in them, and saves the female a lot of energy too and prevents her from giving birth to fry which probably wouldn't survive etc. However guppy's are such avid breeders, they have been known to breed in pretty terrible conditions none the less- its all part of their instinct to survive and breed, since in the wild they are the favourite food of almost every predatory fish in the local habitat, and so guppy's need to breed quickly and a lot on a large scale to help ensure the species survival.
You should always feed your female guppy's a good diet at any point in their life or pregnancy, a varied diet is the best since these fish are opportunistic little insectivores/omnivores. But feeding a good diet is never more important just before and after the female guppy gives birth, as she will need all the energy she can get during these stages- frozen or live foods are a lot more nutritious and easily digestible than dried ones, things like frozen/live bloodworms, krill and daphinia all make good energy foods for small fish like guppy's .
You should also take care that you have more than enough females per male in mixed gender groups of guppy's, and that the tank is not overstocked nor over-crowded and that the tank is cleaned on a regular once weekly basis at the least etc.
Hope this info/thread helps some people, I will add more pics and info later .
Edited by Tokis-Phoenix, 12 November 2007 - 04:31 PM.