Worms Please help

Hi,
I don't want to make this story 2 long, and am struggling a bit as I am using mobile device. I'm afraid it is not discus orientated.
We decided we want to try breeding gyppies(to start with). I had an established 20L tank with 1x10cm common pleco in, and went and bought guppies, and 2 louches as tank mates. After about 10bdays I started suspecting worms. Was told by the few pestshops here, that that is just normal feaces. I have now lost one guppy and am thoroughly unimpressed as I could see the worms on close inspection. I have dosed the tank as per the peprazine thread. We do not have the range of fish products in this country, so was exstatic to find the thread knowing that I have cat dewormer.

My main problem is this: I currently have cherry shrimp in a separate tank, which was meant to be an upgrade for guppies etc in the small tank. I would like to know if the piperazine is in any way dangerous to them.
Obviously their quarantine will be longer than expected, but have concerns that any trace amounts may cause a problem one the rest of the community is sorted.
Thanks in advance.
Sorry it's so long lol.