Aaroz
A point I think needs to be made here is that precipitation, like any other process, is one that takes time (a "kinetic" process if you will). Doesn't have to be a lot of time, but time nonetheless. When a drop of fully saturated calcium hydroxide hits the water, on a microscale there is a HUGE pH spike in the local area, this much is true, and if allowed to sit stagnant without diffusion or active flow would cause precipitation. However, in an aquarium both diffusion and active flow happen. We dose kalkwasser into a high flow area very slowly so the local increase in pH can calcium and alkalinity is dispersed very rapidly -- so fast in fact as to minimize the amount of precipitation that occurs. This is not to say it doesn't happen at all -- it does, it's just not the dominant process when done correctly. Such competing kinetics processes are very common and utilized in the laboratory all the time (e.g. protein refolding by rapid dilution, slow dilution of acids etc.), the key is making sure that the process you want to happen (in this case dilution of the calcium hydroxide) happens faster than the undesirable process (in this case precipitation).
Now, when using calcium hydroxide as a water TREATMENT, it is an entirely different story. I that case, you WANT precipitation to happen, so you add it relatively quickly so that precipitation becomes the dominant process. It's the other side of the competing kinetics problem -- you add it FASTER than the system can dilute it. See the difference?
Now that the science is done, please hear this. There are lots of people on the chemistry forums with different backgrounds -- some people have more expertise than others, but all are welcome and can have valuable contributions to the conversation. Whether their background be formal chemistry education, many years experience in reef aquaria, or whatever else, they are welcome to participate. If you think information being presented is incorrect, please jump in and tell us what you know, even say plainly that certain information is wrong, but take the position of trying to distribute correct information and explain your point of view backed with solid science. Do NOT try and make others feel stupid or less than you.
In just in this little bit of time you've managed to personally insult multiple well respected members of our community, including me by name. And all of a sudden when you found out that I do science for a living that makes me worth your time? You've only been a contributing member here for a very short time, I would suggest a change in attitude.
