I know this may be a bit off topic but there appears to be a genuine concern when treating with PP for the correct dosage. To do that you have to know how much actual water is in your tank. These site links help to do just that. I apologize if these have been posted before or are repeats of other discussions.
http://badmanstropicalfish.com/articles/article35.html
http://www.aquariumfish.net/informat...arithmetic.htm
http://reef.diesyst.com/volcalc/volcalc.html