It's outstanding, and I am hard to sell chemicals to. Protects against ammonia and nitrite spikes up to 1.0 ppm
. And a chlorine remover as well of course. I used it during cycling with fish to protect them. I don't intend to do that anymore but it did protect them. About 95% survived and they endured a couple very bad days of nitrite spike. You can overdose Prime during emergencies. It's just handy to have around at water changes or when things go bad. It's very concentrated so it's truly less expensive than it appears vs competing products.