That's fine... If you actually see them eating it. My shrimp only eat fresh/frozen food like mysis, brine, blood worms, chopped fish etc..
What size tank is the sailfin currently in? Because they need a much larger tank than your 29 gallon... but anyways. Aside from all that... You definitely have a fair amount of rock... I'd say you're going to be able to add up to a dozen hermits to that tank... and yes Emerald crabs like Jay said are awesome too. Not only helpful but really fun to watch.
Now people on here may freak out and tell me that is way too many... but lately I've gone heavy on my hermits and it really helps to keep my tank really clean.
Your tank is new and you won't have much algae on your rocks yet so you'll likely have to supplement some food in the tank in order for them to thrive at first. as well as providing extra shells for them (Just watch your water quality and don't overfeed)
As far as water changes go... I recommend 10% to 15% changed weekly. You should start this now since your tank has just got done cycling you are going to want to remove the excess nitrates. I believe that the strict water changes... especially in a smaller tank has been my only reason for success.
And don't look at adding a Green Mandarin to that tank unless you have an established copepod population... unless you see one at a store eating frozen/prepared foods already. But even if you add them now It will also be unlikely that copepods are going to have an opportunity to establish themselves and take off in the tank with the current presence of the Scooter Blenny.
