Thanks Everybody for your help! My Ph probably crashed because I hadn't kept up with my weekly water changes during my last month of finals. ----3 weeks ago --> I did a 50 % water change and everything seemed fine. The next morning my danios and platys ALL suddenly had a white slime all over body and eyes, and were pretty much belly up. I ran to my local fish expert, he did a water test and there was no Ph. He said that high nitrates (or nitrates?) used up all my Ph. My tap water has 6.8 Ph. I had put all my sick fish in a ten gallon hospital, he prescribed me to add 1 TBS salt PER Gallon (yes this is safe for treatment) within an hour the slime was gone, and all the fish revived and survived. As for the main tank, he told me to add 1/8 TSP ARM and HAMMER brand only (Thus brand buffers the ph, unlike store bought chemicals) Baking Soda PER GALLON per day until the Ph was 7.0. That took one days treatment. Ph has been stable since. ----Back to today, I think I have been doing too many water changes the last couple weeks, but I have not changed filter media and also have a sponge filter in my tank. I have 4 baby platy fry in breeder box that I feed Frozen Hikari Baby brine shrimp and First Bites to about four times a day. Maybe because of this I was over feeding my tank? Thanks for listening...any further advice or comments appreciated!