Dropping KH

[caribou]

I've been injecting CO2 for about two months now. My Ph has dropped, as is expected, but my Kh has been on the slow decrease as well. It was 15 before I started the CO2 and it was at 11 today. My plant is heavily planted and I'm trying to keep my NO3 up. My well water has a Kh of around 18 and I do weekly 50% PWC. I'm dosing NO3 and K. Any ideas why this is happening? My current Ph is 7.0.

 

[Simpte]

Injecting CO2 will lower you KH a bit. Its normal.

 

[Zezmo]

Has perhaps the Kh of your water been dropping because it is winter? Are you regularly testing tap water Kh? or just testing the Tank? Depending on what is buffering your Kh (calcium carbonate?), it may be being consumed by the plants as a nutrient.
If your well is at 18dKh and you are doing 50% weekly changes of only the well water. Then finding your tank at 11dKh would be a big change, esp with your Ph at 7.0 as you indicated.
Test your tank, Test your well water, change your water, test the tank water again. If you write the results down, and do this for several weeks. You should get some idea of what is happening.

 

[malkore]

50% weekly changes should keep the Kh in-line with the tap water. CO2 eats down Kh over a matter of weeks/months without water changes...a few days isn't long enough for that much of a decrease.

You have tested your well water recently?

 

[TankGirl]

You are doing the water changes that should maintain the KH levels, as Malkore pointed out, so I too suspect changes in your KH in the well water, or perhaps an outdated/faulty test kit.

That said, if we are talking dKH here and not ppm, I would not worry terribly much about the apparent drop in KH. You still have plenty.

 

[caribou]

Bingo! My well water tested at 13Kh tonight. Lab tests taken in Oct. had it at 18. I guess the mystery is solved. My test kit is less than a year old but other tests I have used it on seemed a bit skewed so I may have to replace it. Thanks!

 

[malkore]

If they're only skewed a little, and not every time, it's likely just due to different drop sizes coming out of the reagent bottle. Might just wanna make sure the tip gets wiped clean with a paper towel before testing (and avoid using same part of paper towel for each test kit...don't wanna cross contaminate reagents...talk about skewed results...).

I find that a clean tip and holding the bottle perfectly vertical helps with drop size consistency.

I'm glad it turned out to be nothing but changing tap water parameters

 

[PrettyFishies]

What are the desired levels of KH and GH?

I tested my tap water and got 2 for KH and 5/6 for GH

 

[Wizzard~Of~Ozz]

3 is the minimum KH, from then on it's up to they type of fish you have, Tetras prefer soft water(4-6KH), Whereas some chichlids prefer KH 12+ (hard)..

It's easy to increase your KH with Baking soda or Crushed coral, but it's difficult to reduce it (Peat or Water softening pillow)

 

[PrettyFishies]

Well, I'm doing a planted and plan on tetras, swords, cats, a pleco, shrimp and of course, easy and difficult plants....