Yes What did you make the bed out of originally and did you make sure to wait to make sure the bedding isn't still hot as in composting? They will try to get away if the bed is at all warm. Another thing you might of done was use something for bedding that might have synthetic fertilizer in it, as on grass clippings. I found the best medium for starting a worm bed was moistened peat moss and let it cool for a week or so. Introduce the worms and get them working. Feed them some cornmeal everyonce in a while or coffee grounds. Later start giving them your kitchen scraps etc> If there are too many u need to divide them. There might not be enough food for them, Change the bedding too.

The original bedding was coir peat. That was two years ago. I've harvested the castings once in that time. I don't think it's a food problem as I'm pretty vigilant about putting in more food as soon as they become active in the previous lot (I had a problem a little while back of no population growth and Kelly kindly put me straight). I mightn't be vigilant enough though!

Even if there is sufficient food, I imagine that crowding will eventually drive some to look elsewhere. Is this the case?

I suppose, given the dimensions of the bin and the meagre thickness of the castings/bedding, heat could be a problem. The bin is black plastic so heats up pretty quickly.

I'll try rebuilding by adding more coir peat to make their home deeper, if I can find any that doesn't have additives in it. They've started putting things in everything and look at me as if I'm mad when I ask for stuff without the extras!

If that doesn't work then I'll try dividing them, though half will have to go into the cold compost pile. Or I could put them into the hot pile that has now started to cool down.

I am a new vermicomposter, so I'm not going to offer any hard advice, just my own observations.

You came to the right place, since you have a COW (can of worms), you may have the priviledge to speak to SQH1, who is the Goddess of COW. She is super helpful, and I'm sure will reply to your message soon.

You also have Kelly S., who really does not like COW's but is the goddess of everything relating to vermicomposting. She is the end-all of all things wormy. No need to go any further. (Except when inquiring about COW's, which IMHO SQH1 is the end-all).

Now on to my experience (NOT advice!) I have a Wriggly Ranch, which is a 3 layer stacking thing, but is rectangular. I have never had success past the first tier. The one time I added a second tier, it got way stinky and sticky/clumpy so I just removed it all, sorted through it and started again. I don't think this was a good idea as far as cocoons and such go, but it worked in a pinch.

Since then I made a second bin out of a large rubbermaid tote. It seems to be doing much better. The Wriggly ranch still is fine, but it has not increased population like the Rubbermaid has. I split them 50/50, and my rubbermaid is way in the lead, literally teeming with worms, while the wriggly ranch is definitely occupied, but not like the rubbermaid.

I also had problems with the worms getting in the collection bin with my Wriggly Ranch. It bothered me enough to start that rubbermaid bin, which I made with no drainage holes. I just couldn't stand to keep picking them out and putting them back in the working bin. If you want advice on a no-drainage hole system, Mkitten is the one to reply. I think having drainage holes is better for the worms in general, it's just not better for me at this time. And it's working out fine.

You can put landscape fabric between the collection tray and the working bin, this was recommended to me, but I haven't tried it.

I plan to try using the Wriggly ranch as a 'nursery' later. I think when I harvest from the Rubbermaid, instead of going through the castings for cocoons, I'm going to put the harvest in the bottom tray, wait a few weeks then stack the tray either above or below another tier of food. I haven't decided yet.

Oh yeah, you mentioned chlorinated water. I'm assuming that is because you are adding water to the bin. I did that at first, and have now learned that was wrong. I'm in southern California, which is different from your place, but it gets pretty hot and dry in the summer. I added a cup of water a day as recommended in the instructions. That did not work out well. I do not add any water anymore, and have not needed to. In fact, I need to manage the bin to keep it from getting too damp.

Raymondo..Did I understand you have had this bin going for 2 years and never added a 2nd tray? I have many COW's, as well as many other different types of bins. I never did use any of the coir that came with them. I use shredded newspaper/junk mail for bedding. Those bins will heat up very quickly if the sun has any shot at them. Since you only have the one tray above the collection tray, when the bin heats up, the worms are going to head down away from the heat. I will guess that is what is happening with your bin..heat. The worms do not need more depth as they are surface dwellers. When you look in your working tray is the compost above those little notches on the sides? If it is, and perhaps just above, you could add another tray. You just want to be sure the the next 2nd tray you add is in good contact with the first tray. Remove the recognizable food and paper bedding and put that in the 2nd tray. Do not feed that lower tray again, but do check every week or so to make sure the contact is good. I top feed (spread not more than 2" across the whole surface of the working tray) and top with a good 3" layer of shredded paper. I do not mix bedding and food as this can cause heat problems. Crowding is not a problem as the system will self limit, with the population growing to the space and food available. Adding another tray will help build your population. I do not water any of my plastic bins, as drying out is never an issue. With their lids on, evaporation collects on the top and it rains down on itself.

Yes, I've had it two years. It was originally set up for my mother to take care of the dog poop (she has two dogs and complained about smelly rubbish bins). It worked well but for some inexplicable reason she stopped using it. By then it was almost time for a second tier. I took it over, harvested what was there for my mother's ornamentals and took worms and bin to my place. Since then they've had a diet of kitchen scraps. The population didn't grow for me until Kelly pointed out that I was feeding incorrectly. I had been waiting till each lot of food was gone before adding another. This was only a month or so ago. I started doing as she suggested, that is, adding more food as soon as they become active in the previuos lot. The population seemed to explode, well, relatively speaking. Now there's this problem of unwilling inhabitants.
I thought the problem was either heat or overpopulation. But if the population is self-regulating that just leaves heat. The bin, from mid spring through to mid autumn is in full sun until a little after midday. I'll try to rig up more shade for them and hope that the daily routine of moving them back into the working tray ceases.
By the way, the level isn't close yet to the notches in the tray so adding a second tray isn't practical at the moment.
Many thanks for the advice. I'll keep you posted as to progress.

Yesterday afternoon, I checked and the worms had left the working tray and were in the catchment tray. I didn't have time to put them back. Today is cool and overcast and when I went to put the worms back in the working tray, all but one had found their own way back. Quite how I don't know. I think that pretty much confirms that the problem is heat. The bin is getting too hot for them.
Thanks everyone, especially Susan. The worms and I thank you.

If you look at the collection tray of the COW, it has a bumped up place in the middle. The top part of that bumped up area is in contact with the first working tray. It was made that way so straying worms could find their way back up to the working bin. Worms are lousy jumpers!
Yes, it really sounds like heat is the problem. I would find a location where the sun could not find it...whoops..that sounds bad...:)..let's just say place your bins in the shade. Also stop mixing your bedding with the food.

All noted and done. There isn't a shady spot as there are no trees in the yard, well, none that afford shade so yesterday I bought them a beach umbrella. How insane is that? Neighbours thought I was a little loopy before. When they ask what the brightly coloured umbrella is for and I tell it's to shade the worms ....

WELCOME TO WHACKO LAND, Raymondo!..:D