I think what this thread is highlighting is a fundamental lack of understanding of what an ecosystem is and what it means to our tanks and the concept of live rock. Healthy, mature live rock taken straight from the ocean is full of all kinds of beneficial bacteria, algae, sponges, invertebrates, etc, etc. They live on the rock in balanced ratios that are determined by available resources and environmental conditions. All of these organisms are adapted to fulfill certain ecological roles/niches. If the rock is truly mature, it's unlikely that any one of these organisms can dominate because there is too much competition from other species. So you get a very diverse make up of all sorts of organisms living in relative balance with one another.
If you start with a dry piece of rock and place it in the ocean, it will undergo a process known as succession. Early colonizing organisms who are adapted to take over such harsh conditions will quickly inhabit the new rock, they will use available resources on the rock and in the process change the environmental conditions of the rock so that the next round of organisms can move in and take their place. This happens over and over again until a certain balance is reached and the rock is considered "mature." The same process happens with forests after a major forest fire. You start with an empty field with no plants immediately after the fire. Then some early colonizers move in (various wild flowers, grasses, etc), they make the ground more habitable to other organisms (bushes, small trees), the first species of trees then settle in, then the next round of trees, then after many, many years you have a mature, old growth forest again. Google "forest succession" some time if you want to read about how this actually occurs. It's a very well studied subject. Scientists know a lot more about forest succession then they do about coral reef succession because it's easier to study.
My point in bringing all this up is that when you start with dry rock in your tank, it is going to take A LOT longer to reach true maturity then if you start with live rock. I hear people all the time say that they took some dry rock, threw it in their tank for a few weeks, checked a couple of phosphate or nitrate tests and because they read zero they think the rock is "cured" and ready to go. What these people don't understand is that there are many, many more steps to go through before that rock is truly mature. And there's the question of whether or not it can actually reach maturity in captivity at all. All of these "algae problems" that we see in our tanks after using dry rock are simply a product of the succession these rocks are going through as they head towards maturity. I don't know how long that process actually takes, but I believe it is probably years before you get rock that is actually comparable to live rock from a reef. So, if you use dry rock of any kind you need to be aware of this process and realize that your tank is not going to be mature and able to support a healthy captive reef for quite some time after you set it up. Cleaning the rock with acid or pressure washes or whatever is not going to change the fact that this natural succession has to take place in order for there to be a healthy ecosystem in our tanks. That doesn't meant that corals can't grow or you can't have fish, it just means that you are likely to have problems with algae blooms from time to time and other "pests" as these organisms compete for space and resources on your rock. The other problem is that our tanks lack the biodiversity of organisms found in the ocean, so it's a lot easier for an organism to come in and take over on a epidemic scale. We try to be too sterile in our approach and, as a result, if one tiny cell of a diatom or bubble algae gets in, it can instantly explode and take over until something else comes in to compete with it like it would on a natural reef.
With all this being said, I don't know what the magic formula is when it comes to picking live rock for the tank or if it's even possible to reach a true ecological balance in captivity, but I think striving for as much biodiversity as possible and letting the organisms balance themselves in a natural way is probably very important. Algae blooms and other occurrences of "pests" are bound to happen in virtually every tank. It's part of the hobby.
