I tend to disagree that a scooter is any easier to keep than a mandarin. I have both a scooter and a mandarin, I got the scooter to eat prepared foods almost right away, the mandarin in my 55, dont flame me, the tank is only a month and a half old, with about 30 pounds of rock, is doing great and im concerned hes getting a little too fat. This tank dosnt have a tremendous amount of pods, but has a breeding population of mysis shrimp. I dont think tank size, amount of LR, ect. has as muc to do with whether or not you can keep a mandy, and more to do with the research you put into keeping one, experience, and fauna in the sand and rock in your tank. Having say 100 pounds of LR dosnt mean you have tons of pods, true they have more room to colonate, but that dosnt mean they will
In the past I have kept two other mandys, one in a 29 that was established for 2 years and the mandy was fine for the entire time, until that is my top off system opened up and dumped a few gallons of fresh water into the tank, dropping the salinty drastically, and the mandy jumped, another I had in my 75 with over 150 pounds of live rock and it slowly starved to death
According to everyones opinion the mandy in the 29 should have starved and the one in the 75 should have thrived
Now Im not saying you should go out and buy a mandy, Im simply saying there are more variables that tank size and the amount of rock you have. HTH