Well, it's been a while since I promised an update. One way and another, it has not been a good winter for me. However things are now looking up!. It is now 9 months since I put the wormer in the tank, and the shrimps are thriving. There must be about 40, and I will shortly be extending the gene pool with a new addition or two.
So, I ran a load of carbon as Sue suggested, and threw it away afterwards. I daren't clean the glass because there are always a lot of baby shrimps on it having "lunch". After 9 months, and many, many water changes, I reasoned that the shrimplets will have eaten and "processed" the copper from the wormer, and the w/c's will have removed it. (Yes, I should have listened!)
I had bought 4 zebra nerites for my 125L, with the eventual intention of adding one of them to the shrimpery, when they had had a month or so cleaning the glass. They did an excellent job. So, one was transferred. For two weeks it hoovered away, doing a sterling job. Then, like before, it slowed down, and spent a lot of time half out of the water, rarely moving. I contemplated putting it back in the 125L, but before I could, and after 3 weeks, I found it on it's back in the tank, not moving, presumably dead. I removed it to a jug of 125L water and waited. To my surprise, after some 6 hours, it had moved a little. The next morning, it was on the side of the jug. It was returned to the 125L, near to the front glass, where I could see it. It very slowly made it's way to the glass, and stayed there for a week. If it moved 3 inches in that time, that would be an exaggeration. I never saw it eat, but it did lay 2 eggs!
Then, it slowly started to move, and feed a little. Now, another week later, it is zooming around the tank, just like before. I think this was a very close shave - either that, or I have been well and truly conned by a pregnant snail! I have ordered some Arcadia Polyfilter (as Sue suggested, of course), and will use that until it's gone. Then, perhaps, I will try one of the other nerites ......... unless, of course ........ you know a better solution?
Skittler