This is not intended to step on anyone's toes, so I hope it is not seen as such. Prime is a product that detoxifies ammonia, nitrite, and nitrate, which allows for easier removal by the already established aquarium biological population. It also removes chlorine/chloramines and adds a protective slime layer. So, while Prime is a temp. solution to high levels, it will only really save fish in an established aquarium, as pointed out already. It's not really economical to keep adding prime to the tank that's not anywhere near cycled. Plus, and I may be wrong, but I know that some of the slime-layer enhancing products make skimmers go insane. If the tank is already established, it's a great product. It saved my little african cichlids that had a medication crash their tank's bacterial populace. And now with nightmarish flashbacks to that, I'm off to watch Finding Nemo.
125 gallon saltwater: 55gal sump, 4 Blue-Green Chromis, Purple Tang, True Perc, Firefish, Royal Gramma, 5 Ricordea, Bubble Coral, 15 Pulsing Xenia, Green Star Polyps, Deresa clam, Green-Tip Torch Coral (about 11 "heads"!), Orange Montipora Cap, Purple M. Digitata, Green Slimer Acro. Yongei, 3 Orange M. Digitata, Pink&Green Acro. Millepora