It's clear not everyone likes the idea of using water from a local reef shop's display tank.
- Some people think you can "get something," which I admit is possible if the source tank is unhealthy. That is why I - in a case like this where a system is potentially crashing - suggested finding a local reef shop with a display tank that has been healthy for years and is not connected to the stock tanks. These tanks represent a shop's "best effort," and for some hobbyists here to "fear" a shop's best effort is laughable.
- Others think it's not necessary to buy seeded water because they feel a 100% water change would not lead to a cycle. I agree it's possible the tank won't cycle. But IMO, it's too dangerous if the tank is already experiencing die-off. In a tank that is having such serious problems that a 100% water change is required, we can usually assume the hobbyist needs some help. Relinquishing control to a reef shop's "best effort" is not a bad idea in these cases.
- Some people simply say "you just don't do it." It's sort of like Belichek going for it on 4th down inside his own 20 with 2 minutes left when he is winning - you just don't do it (Im guilty of thinking this way sometimes). It's like there is something inbedded in fresh and saltwater husbandry doctrine, and some people don't even ask "why."
But in the grand scheme of things, whether or not you like the idea of using water from a LFS display tank, I think you have to entertain this option when you consider the alternative. And when I say "the alternative," I'm referring to the practices of some reefkeepers. In my mind, the risk of possibly introducing something bad to the tank is an easy call to make when you consider some of these guys are using dechlorinated tap water, not testing RO before mixing, not testing for PH after making a new batch, not heating the water before adding, not cleaning their mixing supplies, not using quality salt, under-mixing the salt, not cleaning their hands before handling new batches, OR cleaning hands with soap and THEN handling new batches, or mixing water for 5 minutes and then adding it, etc etc etc...
Many people that have tank issues bring them upon themselves, and they could do A LOT worse than letting their local reef shop provide them with healthy, cycled water.