You have read up. Apparently my reputation preceeds me (not always a good thing I might add).
Just to be totally honest I am NOT into "Speed Cycling" but at the same time I have to admit my wife's tank "Speed Cycled" whether I like it or not
One reason why we suggest you wait "long term" for these is because they demand VERY stable and high quality water conditions. They don't tolerate change very well at all and need the highest quality water you can provide.
Since you admit you're a "Noob" that gives great concern to short term stability. You have to learn certain things and unfortunately some of those "lessons" will be from mistakes. It's not that a NOOB can NOT maintain high water quality but there are so many variables that affect water quality that it's hard to mentally grasp them all. That's a key reason why they need a well established tank. Given the fact we are talking about a "Nano" tank that just increases the "Err" factor substantially.
Also take into account that when/if (honestly more likely when) that critter expires it will easily and quickly "Nuke" your tank. With less than 20g of water to work with it will be very easy and quick to get out of whack. Trust me when I Say... when it does it's NOT pretty.. NOT easy and usually NOT CHEAP! I had a simple little $8 critter nuke my tank in just a matter of hours and I can't tell you how much I lost in CORALS! I lost a VERY nice (and large) Finger Leather that was AWESOME! If only I had know then.....
But alas there's really not much you can do if you can't "unload" it. I can tell you one thing I WOULD do.... If I woke up in your shoes I can assure you I would NOT set foot in that LPS ever again. If they can't help me when I need them most... then they don't NEED my money or my good words about them. My money is too hard to come by to give it to someone who isn't willing to help me out. I'd turn my back on him and make sure ANYONE who would listen to me would know exactly how "Pops" treated me when I needed some help.
Hope that doesn't come off as TOO harsh but I'm more about telling you what you NEED to hear rather than "Sugar coating" it hoping you will eventually get the truth. I've been there.. got the T-shirt and hat!!
Good luck buddy! Remember Life Is GOOD
