I used PRZ for fish (aquariums) purchased online at the auction site. They come in various sizes. Powder is bitterly nasty-tasting and best put into capsules. I have had no problem using any of the veterinary meds and have successfully used horse, goat, dog, fish, cattle and poultry wormers. Just keep an eye on dosage as sometimes a human sized dose is quite big when using small bird or fish wormers.