Depending on the situation, grinder pumps have their place. I prefer not to use them and use a solids handling pump if possible. I would not use any additives for a grinder pump. Anything can be messed up if you abuse it. I would not flush rocks, cans and wire down the toilet. If the alarm is going off it could be something simple like the floats need to be adjusted or expensive like a primary pump is not working in a duplex system. There are so many possibilities. It is hard to answer your question without more information such as are you on city sewer or a septic system or some type of alternative system. Is the pump pumping sewage or something else such as ground water? Is the system located in the basement or in the crawl space or out in the yard etc.?