I usually put a couple shrimp in a media bag and throw it in and let it decay till it's pretty much gone. Can take a couple weeks but have used that method a few times and recently on my 225 that started with dry rock and sand with success. Takes more time than dosing but it works for me. I've definitely learned patience from this hobby so it's no big deal for me. Go with your gut tells you, the most important thing is testing anyway. As long as you go through the cycle the results will end up the same.