The SL Aqua is a herbal extract so isn't actually a chemical and it had NO negative impact (they say maybe snails would die but mine didn't) so ultra simple, quick and effective. Mine was a new tank so there were only snails living in the tank at that time. The hydra I had were so tiny (tank was only a few weeks old so they were probably young) you needed a magnifying glass to see them and it would be quite difficult to remove them without disturbing the aquascaping as they were attached to wood (that is probably where they came from)!
I have seen the traps on ebay but I don't know whether they are effective or not, but they don't look nice in the tank and how do you know if/when you have caught them all?
I think the SL Aqua Z1 would definitely be the way to go if you have hydra/planaria and you can get hold of it, it is a natural product and couldn't be easier, 1 dose and you should be done, though they say you may need to do another, but I didn't, though I doubt there were that many in my tank anyway!
Hope everything is going well with your shrimp tanks kms? I haven't seen many of my new shrimps (3 so far today, early yet though) but it is a heavily planted tank and they are adolescent size shrimps. I have put some fresh spinach and a pea in there today, hopefully that should draw them out? I checked the parameters etc yesterday and they were all spot on.
Simon