Guppy sexing question

[sducky]

A few months ago someone offered me an absolutely beautiful male cobra guppy and a couple of pretty yellow females with orange tails. In a total lapse of judgment, I took them, and predictably, I now have more guppies than I know what to do with.

I kept the babies in the tank with the adults and a lot of them got eaten, but I still ended up with about 40 juveniles. I took those out of the main tank and set up 2 ten gallon tanks, and I did my best to separate them into male and female, but I was really bad at it. All the Youtube videos made it look so easy, but when I tried it they all looked like females to me. So instead I put all the totally plain ones in one tank and all the ones that had any hint of color in the other, knowing that wasn't really the way to do it.

Now they're all bigger, and I can't keep them in two 10-gallon tanks any more. All these people online who said you can sell them to your LFS are out of their minds - none of the stores near me will even take them for free. So I decided the thing to do is, spread all of the males between the several tanks I have. Then for the females, I can buy a new 50-gallon tank, and put them in there with some ghost shrimp and dwarf gouramis that will eat most of the new fry. (Then when the guppy population eventually dies off of old age, I have one nice big tank and I can gradually start reducing the number of tanks I have, which has gotten kind of excessive.)

But of course, that meant I had to take another shot at sexing the fish. They're bigger now, so you can see the anal fins a lot better, and some of them have started to develop nice colors. But as I started trying to sex them again, they still looked almost all female to me. Out of 40-odd fish, only 8 of them were unmistakably male (with the elongated anal fin that they tuck in like they're ashamed of it). Even some of the really pretty ones had the triangle-shaped anal fin when I looked at them closely. And aside from two really spectacular ones, the males weren't necessarily the most colorful of the bunch.

So my question is: is it possible I have that many females, or am I just really bad at this sexing thing? I think I've read that with some amphibians, water temperature and chemistry can effect the gender of the babies. Could that be true with guppies? What do you think is going on here?

 

[Delapool]

Water temperature rings a dim bell somewhere. Will see if I can find anything.

You could run an experiment and see how accurate you are over time?

 

[54seaweed]

the female has a rounded lower fin , the male has a hook like fin .
here are 2 diagrams to better help you understand what to look for .

 

[sducky]

Actually, I spent some time researching a variety of forums online, and apparently it's pretty common to have mostly females, with only a few males. (I guess that makes sense biologically, as you only need a few males to impregnate a lot of females.)
Some people claimed water temperature and pH affected it, but there wasn't any agreement about the details. And some people claimed that if you leave the fry in the tank with the adult fish, the survivors will be mostly female... I assume because the females get bigger faster.

Funny thing - if my fish are mostly female, then I was actually pretty good at picking out the males when I made my first attempt at sorting them. I put all of them in the same tank except for one. Unfortunately, I was so sure I was getting it wrong, I gave up in the end and just distributed the females between the two juvenile tanks. (Doh!)

 

[sducky]

Yes, that looks like the diagrams I used. 8 males and about 40 females, which I thought was suspicious. But based on some other sources I found online, it's not.