This seems like a dumb question when the bottle comes with instructions, but I have one issue: this stuff seems like it's really concentrated, and my tanks are not even close to the size that the instructions talk about. I'm sure I'm not the only one who just has tanks that are 20 gallons or below and wants to use Prime. So how much Prime do y'all use per gallon and how do you go about measuring that out properly? Also, how much of an issue is it if you overdose on prime? I don't wanna hurt my fish by accident.