| | Why Water Became So Acid?
Our tap water is very alkaline, about 7.4 or 7.6, and the water in my 29-gallon tank used to be the same. In recent months, however, it has become very acid, about 6.4 or whatever the lowest number on the pH test registers. I am trying to figure out why.
I have reduced the frequency of my partial water changes and gravel vacuum, from every 2 weeks to every 5 or 6 weeks. I think the gunk in the gravel helps the plant growth. I also added a couple root tabs, and the swordplant is finally thriving. When I kept the tank too clean, the swords got punnier and withered away.
Water test results: ammonia - 0 to .025. Nitrite-0. Nitrate-80. Total hardness-120. Alkalinity-80
The plants are growing now, and the fish seem healthy in general. I notice the cherry barbs don't seem to eat as vigorously as they used to.
So my questions are, what causes the acid water, and what should I do about it? Maybe 25 percent water changes every 2 weeks? I hesitate to do a big water change, because of ammonia toxicity if water suddenly becomes more alkaline.
Thanks for any help or suggestions.