We have gone a year with changing water, putting in guppies and snails. Both guppies and snails having babies, etc. Haven't had much in problems except we saw the ammonia spike a couple of times.
In the last 2 months we keep seeing the pH go drasticly down. One day is it looking good and the next wow down to 6.2, the last bad spike was somewhere between 5 and 5.5. Today we were at 6.2 and we added baking soda like we did the other times. The time it got to 5-5.5 we lost all my males. It was fine that morning and when we looked at about 7 that evening we had dead guppies. We got some of them out of it into a tank that was still looking good and some rallied for a day but eventually we lost every male we had (only males were in that tank). This month it has gone down twice so far. We are managing to go through a whole box of baking soda.
Stats: our water is very hard and before we put it in the tank it usually is around 7.4 - 7.9 pH. The only thing that has changed since a little before we lost all the male guppies is that we went from using "startzyme" to "aqueon water conditioner" and started using liquid calcium " Kent marine calcium" that our fish place recommended, instead of a hard calcium tablet.
So does anyone have any idea what might be causing this.