@Ari Almassi, I do think that we all can get caught up in the weeds a bit and try to control parameters too much. Have you ever snorkeled or dived on the reefs on the Big Island of Hawaii? If you ever do, you will notice that there is an abundance of fresh water coming from the lava rock beneath the reef from rain run-off. The salinity difference is so great, you can see the fresh water vs the salt water. Even in that environment, there are corals that are flourishing and tons of fish. So, I don't think your inhabitants will care too much if your salinity is 34 ppt or 36 ppt. As long as it stays consistent, which it should with an ATO, you will be fine.So the salinity being off by 1 or 2 points doesn't matter? This is a surprising answer to be honest. I always figured to have the best chance of success you really need to have a stable/accurate salinity in the tank. When you mention that constant proportions of seawater don't apply in aquariums, why is that?