pH Crashes

[Aienu]

I have a 60 gallon tank with the following:
3 neon blue dwarf gouramis
2 paradise gouramis
1 cinnamon dwarf gourami
4 silver dollars
2 gold gouramis

The nitrite and nitrate levels are fine, the ammonia is fine, but my pH has again crashed to an acidic level (much yellower than the 6.0 that my test kit goes to). I did a 50% water change 3 weeks ago. There is a Tetrafin filter which I changed both cartridges to the last time it crashed (3 weeks ago when I did the water change) and an undergravel filter with 2 powerheads. I was told to use baking soda over a period of several days to slowly raise the KH level, does anyone have any experience with this method or have any alternate ideas?

 

[mrV]

You should do water changes weekly, then there isn't so much harmful compounds in water and probably the pH keep steady.

Bakind soda (NaHCO3) increases carbonate hardness. KH should be at least 2 in normal tanks. When adding NaHCO3 also pH increases.

 

[Alien Anna]

Tufa rock is great for raising KH and thus keeping your pH stable, without causing wild pH swings.