Yes, eddie is right... the big determination is going to be in the type of fish, water quality params, and any other symptoms.
Suggesting medications without knowing the species of fish and what shares the tank can be deadly. Suggesting meds without knowing water params can also be deadly. There are a lot of IP medications out there, but not all are safe for all fish. If one medication were effective and safe for all, there would be no need for another, correct? Both medications that were mentioned were good meds, but again, not safe for all fish.
Jinith, can you please provide us with the information, so we can help you safely? White poo without any other symptoms could be nothing at all, and to medicate "just in case", think of it as giving a child cough syrup everytime they looked like they might cough, or had a scratchy throat. Would that be helpful? Just as with people, if medications are used when not really needed, fish's bodies and the parasites themselves will begin to develop an immunity to that medication. Then, when something bad hits, nothing on the open market will treat it, because its immune to the specific active ingredients that these products have in common.
My suggestion right now would be to get us more information and lets first determine the fish is really sick before wasting money on medications that could do more harm than anything else. If in doubt about a fish's health, move it to a quarantine tank by itself, then determine the problem and how to treat it.