Guessing age roughly from size?

Hello, this is possibly a silly questions...

I have read on the caudata care sheet that terrestrial juveniles take between 1 and 3 years to reach sexual maturity which i'm guessing means their adult life! So as there is quite a big range between 1 and 3 will I not be able to guess age by size?

I have absolutely no idea how old the three newts I have bought from the aquatic store are (the man in this particular store could not tell me for certain)

And yes I know now they are most likely to be wild caught so I don't need to be told again...

I have them in a planted aquarium (25 plants + floating plants) and I have just ordered another 25 plants on ebay to really make it heavily planted for them.

I also have a turtle dock but they don't seem to be using it at all - can I make the assumption for this that they are already 'adults' if they are spending all (or most- maybe they sneak up to the turtle dock when im not looking haha) time in the water?

They most definitely are wild-caught, hold no doubt about that (i´m not trying to be rude, just trying to inform you).

You can´t tell the age judging by size, for example a 5cm long newt can be either 9 months old or 3 years old...
If they are fully aquatic and pet-shop bought, then they are adult, and that means there´s no way of even making an aproximation.
Good choice with the plants, they love VERY heavily planted tanks.

Thanks azhael... Gave them their first live feed of brine shrimp this afternoon, extremely pleased they started gobbling them up as soon as they went into the tank! Are newts poorly sighted? It seems they only really take notice of the shrimp when they are right infront of their faces - maybe they're just lazy...

Yeah xD they don´t have good sight. They locate prey mainly by movement and smell, and that only works well in close range as you have witnessed. Live brine shrimp is an excelent food, well done.

Be careful with plants on ebay...definitely quarantine them for at least 30 days...mass producers of aquatic plants don't really provide the best care, so give them some time before you put them in with the newts.

Hmm well its a bit late now as they are already in with the newts and I'm not sure where I would quarantine them. I have never had problems buying them off ebay before in the past, bought them for aquariums back at my folks house... Thanks for the info though - what is it they would likely pass on to the newts?!