UV steriliser is good it means you won't have whitespot (UV kills this parasite). Flukes you cannot see with the naked eye, need a microscope. Prazi won't hurt the plants or the biofilter. It's also a wormer which is nice. You'd have to get some from a vet if anywhere. You should also be able to get stronger formalin from the vet (40% as opposed to 5% from LFS). PP is easier to get, most pharmacies will have it.