Every tank I have started in the last 30+ years with exception of one was started with well cured live rock. That still doesn't have much of a bearing on the tank maturing and even with the use of liverock, it still typically takes a year or more for a tank to fully mature.. It's par for cours regardless of whether you use live rock or not. Live rock without a decent load will loose bacterial populations. Those populations increase and decrease gradually based on the biological load. Bacterial populations diversify over time and it's not just the rock where the bacteria populates. Every surface of the tank and sump become places for bacteria to colonize and diversify. Live rock is a great source for more diverse bacteria but it will also have some die off when transferred from one tank to the next. Anaerobic bacteria will die off as just one example because air gets into the rock killing off the anaerobic bacteria which is one of the main denitrifying bacteria's. Water chemistry changes over time. Not just in a couple months but over the first several months or more. These are all parts of the changes a tank will go through in route to becoming fully mature and while we can't measure those changes, those changes have a direct impact on the inhabitants in the tank and various sensitive fish species, corals and invertebrates don't tolerate those kinds of changes well.
I was not trying to be a "œdouche". I am sorry you feel that way but I don't think my response warranted name calling. I've been in this hobby a LONG time and ultimately was trying to help since I have experience with BOTH fish. I could have omitted that first sentence but I am sure I stated what many experienced hobbyist here were thinking. It's a common mistake that people new to the hobby make when it comes to those kinds of fish. And frankly, I was trying to help and save you grief, frustration and money down the line not to mention unnecessary fish casualties. I was not trying to rub anything in your face.
If you read up on sailfin tangs on this forum or elsewhere on line by doing a simple google search, you will find that pretty much all reputable sites suggest a very large aquarium for that particular tang and for good reason. I've had them before over the years and frankly, I won't even put one in my 500 gallon display because of their territorial and agressive nature. If you do a google search on Garden Eels, you will find the same information I provided. They require much larger tanks with very deep sand beds and even then, they are hard to keep successfully.
So I apologize if my response to you made me a "œdouche". That certainly wasn't my intent. I was only trying to help you and share information that others were not providing.
