I'm with Izzy. And i just took a look in your log at the 30g which i assume is this tank, since you asked about the pH in the comments there too.
You have soft water fish, so letting the pH lower naturally will not cause trouble. It can get too low of course, but let's not worry about that just yet. First we need some reliable data, as Izzy mentioned. You should have a pH liquid test kit, API is a good brand that most of us seem to use.
We also need to know the hardness, the GH (general hardness) and KH (carbonate hardness, or Alkalinity). The GH is just as important for fish as the pH. The KH/Alkalinity will buffer the pH to prevent it from shifting, so we need to know this in order to gage what the pH may or may not do over time. In any aquarium the pH will tend to lower gradually, due to organics and such, unless there is something targeting it that keeps it from doing this. You can ascertain the GH and Alkalinity from your water supply folks, they may have a website with water data posted, or they can tell you.
Once we know the GH, KH/Alkalinity and accurate pH of your tap water, we will have a better idea of things.
And I will reiterate what Izzy said, don't use chemicals to fiddle with pH. Not only is this bad for the fish for several reasons, it may not work due to the KH and other factors.
If you want to read more detail on all this, here's an article: http://www.tropicalfishkeeping.com/f...quarium-73276/
Post the above numbers for the tap water, and the pH for the tank water (tank GH and KH doesn't matter here, as the article should explain), and we'll go from there.