Let me be a little more specific about my future plans (I probably should have included this in my original post). I have every intention of adding a 135 gallon aquarium to my collection in about 2 years. At that time, the larger fish (mainly the domino and three striped damsels) will be moved to the new tank. That's what I've done with my freshwater tanks since the start and it has worked out fairly well for me.
About 3-4 years ago I started off with a tiny 5 gallon tank that would be considered overstocked by most aquarists. I had a baby goldfish, a mollie, a catfish, a betta, and a pleco in that tank. At this point I'm sure you're all thinking the goldfish would have killed everyone else in the tank once he got a little bigger than them, but that was never the case. I think that since he grew up with everyone else, he had no problems with them and since there was no competition for food, they all coexisted happily. I had enough filtration to take care of their wates and I performed maintenance often enough to where the fish were always happy. Naturally, after about a year these inhabitants outgrew their tank (mostly the goldfish and pleco) so I grabbed a new 10 gallon tank and moved those two out of the 5 and into the 10 and added a couple other fish into that tank to a point most people would consider overstocked, but once again routine care and way more filtration that I needed kept everything running smoothly. Over another year or two the 10 gallon was outgrown so I got a new 30 gallon, combined the 5 and 10 into the 30, added some more fish, and now the 30 has been hapilly trotting along for about a year (recent picture below).
I took the picture on my phone so the quality is horrible, but that gives you an idea... There are 26 fish in there (including a discus, angelfish, plecos, and a few other larger fish like that) which most would consider extremely overstocked for a 30 gallon tank, but the fish are perfectly happy. I have filtration recommended for up to a 110 gallon tank on there and the water is spotless. There are a bunch of hiding places inside/behind the rock and in the plants and I've noticed the fish tend to take turns. One fish will go hide in a plant and hang out for a little while, then come back an hour or two later and when he comes out, another fish will casually stroll into that plant and hang out for a little while, and the cycle continues. It seems thats the way it is with all of the hiding places. There hasn't been one death in the tank in the past year or even as much as a stressed looking fish. They're all eating great and get along very well.
In my mind I was thinking that all aquariums, both fresh and salt, were this way... as long as you went way overboard on the filtration, provided plently of hiding places or just spaces to relax, and got tankmates that could all coexist peacefully, then "overstocking" isn't really a problem as long as the fish still have plenty of open space to swim.
I was planning on running the saltwater tank in the same way... overstocking it and when some inhabitants get too big, getting a larger tank and transferring them to that one. I figured 6 damsels was just the start and I'd get a few clownfish, some anemones, some coral, angelfish and a tang as well. Now I'm kind of at a loss on what to do... Here is a picture of the saltwater tank as it stands right now.
Again... horrible picture quality, but you get the idea