Quick side note about the little towers is that they do seem to degrade over time and if the sandpaper touches the wet soil it will disintegrate. So try to avoid watering the devices themselves if you can. Don't think this helps much.
I know the feeling with the copper! Have also run out...
Some cool looking ring magnets arrived today however and will be conducting tests immediately to see if they have any effect on plants growing in the centre.
I have made a dozen of them and I was thinking just that. I water with a hose, so it will be short lived experiment. I wanna make good quality permanent ones anyway as soon as I get to it.
ring magnets ? as in large round magnets that fit around a plant ?
I suppose the little ones can go over a Lakhovsky coil.. never thought of trying that before..
wishing you a good Sunday !