I completely agree. People keep saying you can't, you can't, you can't. Obviously it stems from not wanting to spend money on more and more things. I think the most successful tank is one where homeostasis occurs and survival of the fittest. I am adding an arrow crab and a false perc to my tank today. I have a bigger marroon. Hey if the marroon kills the perc oh well, if not it will be a cool combination in the tank and people will enjoy it. Similarly, if the arrow crab catches a fish, oh well, guess that fish should have been swimming faster. Now I understand the capabilities of what my size reef can hold, so if the arrow crab grows large, then its not a matter of homeostasis, its a matter of needing a larger environment and I can trade him in for a new mix. Or smaller arrow crab and start again.