jaybird002

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.

Jon

AaronT

This.

I gather you are not adding CO2? Your KH is being used by your plants as a carbon source. This is normal and nothing to worry about. If you were adding CO2 it would happen slower or not at all.

Most plants love a pH of 6.4 or even a little less so don't worry about it. I wouldn't say it's very acid, very acid is in the 5s or lower.

mariannep

Personally, I think 6 point something to 7 point quite a bit is "normal range": Anything above or below that I'd watch, because it'd be preferred by plants and fish adapted to acid/alkaline conditions. Also, I believe ph fluctuates during the day/night, becoming higher as plants take out C02 from the water. So time of day is a factor, too.

I'd try to see if anything else could be affecting the cherry barbs. Maybe they're even just more relaxed... but I never had them so no idea if that's possible...