Yes, I think a magnifying glass would work fine....you just want to have a very close look at the negatives. My tanks have a thermometer that you twist to agitate. I think I do 30 seconds initially and then 5 seconds every minute (someone else might have some better procedure.) With other tanks they agitate by turning over and back. (there are videos on you tube.) I hope an experienced person can answer you last question...doesn't make sense that 23 no good and 1 good.