I use a Walmart 10g with an Aquaclear filter for my QT tank. I do about 20-25% water changes, but it's with the water from my main tank when I do its water change. I've never had detectable levels of nitrites or nitrates, much less ammonia. I've only tried hypo as a preventative measure once and I lost the fish. It probably wasn't a result (at least not directly) of the hypo, but it makes me nervous now. Many very experienced reefers always use hypo as a preemptive treatment for new fish.