pistol shrimp+yellow watchman + live rock question

I just acquired a pistol shrimp and a yellow watchman goby yesterday and this morning i got up and turned on the lights, they are already paired. However, they took a middle column of the tank and are hiding between rocks in the middle, I'm a little bit concerned about them not being able to get food because I do several small feedings a day, and they might not get any food because of the clown fish, yellow tang and a singapore angel in the tank. Should I use a syringe and bring some food close to their burrow or they will manage to find food themselves? Another question is, is it okay to add live rock to an established tank? The live rock that the local stores sell have lots of living or dead things on the rocks, I don't want to bring ammonia into an already established tank.. And if i was to add, and add a few pieces at a time, will that be okay? thanks in advance

 

Use a feeding tube. Or a turkey bester. This way you can feed them directly