Like Johnny said ,it would be best to get your own liquid test set.
It'll come in handy, whenever you fear something might be wrong with your oscar.
And i can tell you, we oscar keepers can worry a lot.
I doubted my fishkeepingskills on several occassions, but the test results gave me peace of mind.
Plus when emergencies come up, you'll be able to see what steps need to be taken.
As for the sinking pellets, you can try that, allthough it is my expierience that oscars will take any food you offer, once they have settled in and are feeling at home.
Just sit by your tank and fish, talk to him and let him get used to your presense.
He'll come running like a puppy in some days.