Sexing Chinese fire belly newts

[commoner]

As mentioned in the title, I found it is very difficult to determine the sex of the newts, especially in their non-breeding period. By far what i know is that males would have a prominent, larger cloaca, as well as finned blunt tail. Is there other sexing method for firebelly newts? If possible, i would like someone to sex my newts (a side question: In what way can i feed frozen bloodworms in order to minimize the pollution of water?)

Here are some photos of my newts

 

[AuSu]

There might be two boys in the pictures on left as their tails look short compared to body length. On the right pic, newt in the left might be girl looking at the tail length. But these are just guesses made by my notifications on my own newts!!! If you have any better pics, I think someone will be able to help you be sure. Are they still quite young? Maybe they could eat a little more or is the photo just making them look like that? If you can find some, earth worms would be the best option for food. I don't know if there is a way to feed bloodworms "clean", I feel they always mess. Some people rinse them to decrease it. But they are quite low in nutritional value so they should be just a nice snack every now and then, not a common meal.

 

[AuSu]

Talking to myself...it seems the pictures show up in different order in my phone. Now that I'm using computer I'd say at least the newt in third picture is male. Also many of the others look males, but if you have better pictures about tails (length and end shape), that would help! How many are there alltogether? These five or more?