I assume you are talking about the phoenix worms, if you buy them online they tend to not be very fat even the adult ones but if you gutload them (which can get gross) they get very plump.
Here a blog I made comparing feeders with a printable chart
https://www.chameleonforums.com/blogs/bbprinting/817-nutrional-information-your-feeders.html
They look like pop rivets. The site shows you have to remove them also lots of youtube videos
http://www.doityourself.com/stry/how-to-remove-a-pop-rivet#.Uf3Dsqx2HFw
I created a blog with a more detailed breakdown and printable chart
https://www.chameleonforums.com/blogs/bbprinting/817-nutrional-information-your-feeders.html
Most people don't gut load them because they have so much calcium but you can it just gets nasty. Plus if you gutload they become much bigger and are therefore more filling and more nutritious. Depending on how many you have you can put about 50 in a coffee can and then put any normal gutload...
You can get small phoenix worms to feed him, I have a 3 month old also and I think it depends on the phoenix worm, the ones you get in a cup are not very fat so a full grown phoenix worm would be fine but I feed my phoenix worms so they are very fat and are probably too big for him.
Once they get solid black they stop eating and begin to move to higher ground to try to find a place to convert into the flys. If I was you I would put a bunch in a feeder cup in the chameleon cage where no mist can hit it. Then wait and see if they hatch, if no water hits them they will not rot...
No nothing but bad reviews on this stuff, you just can't beat doing your own gutload. You can make enough and freeze most of it and make it last for months.
Here's Sandra's
good info on gutloading:
https://www.chameleonforums.com/blogs...utloading.html...