water very acidic

[michelliot]

After noticing that the majoity of my fish population was swimming near the surface of my twenty gallon tank I decided to do a barage of tests. Every thing was normal except my pH test showed a level of 6.0 which was not the norm. I immediately did a partial water change and tested the water going in (around 7). I tested the water in the tank again about a half hour later and the level was just below 7. About 3 hrs later the level of the water was back down to 6 again. Never had this problem before. Have not changed anything except the filter pad carbon in my penguin 125 about a week ago (first time with new carbon bag). Same fish population, no plants or chemicals added. What could make the acid rise so quickly? Hope I could solve this quickly. Please help with any suggestions. Thanks so much

Elliot •¿•

[michelliot]

I think I just solved the problem. I believe it WAS the carbon. I added some to some tap water in a glass after checking the water itself (about 7). The carbonized water was down around 6 again. Is this normal? Should the carbon be sooo acidic. I bought it by the bag to save a few bucks by stuffing it into the pads each month. Are there different types? Also, will the tank neutralize itself or should I do something for it. Don't leave me guys, I still need some help. THANKS AGAIN !!

Elliot •¿•

[Skittyfish]

Check your kh and gh.

[wetmanNY]

What did it say on the bag?

[michelliot]

Actually did another 25% water change last night and did not put back the filter pad with the new carbon in it but used a standard replacement pad. PH immediately rose to around 6.5 and has remained there this morning. It had to be that bag of carbon. Don't want to be drastic with the pH changes so I'll probably do another 25% change in a couple of days. Thanks for all of the responses. Speak to you all soon.

Elliot •¿•

[wetmanNY]

I wonder what it said on that bag of carbon? Maybe it was just an unmarked gunny sack. Maybe Eliot didn't rinse the bagful of carbon before it went into the tank. Maybe I should try with my own (name-brand) activated carbon...

[RTR]

If it stated - and you can bet it did not - it would have said phosphoric acid washed. Dark ages stuff.

[michelliot]

YES, after reading it, it was a local brand, but it was packaged for aquarium filtering. I'll try and return it to my LFS in exchange for some Blackdiamond or Aquarium Phamaceuticals brand. Only used about a quarter of a cup so if they're willing to sell it, they should be willing to use it.

By the way, the fish tank has equalized to normal pH and all the little guys seem to be unscathed.

Thanks
Elliot •¿•

[wetmanNY]

Elliot, since your pH is easily shifted, your alkalinity ("KH") may be very low. Better test it. You can strengthen your carbonate buffer with a teaspoon or so of crushed coral in your filter.