I have been using them for over 2 months (Total with phosphate). $10 for 75 pellets. I don't use the injector. If you have a high tech tank with plants tend to hog one particular nutrient, you may still want to dose your water column as well. I feel that the pellet does not have "enough" composition to deal with fast growing, nutrient hogging plants such as Temple plant, and Amazon Sword. You may need to double dose the pellets. The good thing is that you get 75 pellets and so you can dose very liberally. It does not alter your water parameters.