# diminishing kh



## anubias6439 (Sep 7, 2010)

A question has been wandering through my head today - 

With a well maintained (regular water changes/filter maintenance, etc.) aquarium that has CO2 injection, does the Kh value decrease faster than that of an aquarium with no CO2 injection?

I ask this because kh is the buffering capacity of the water. The only thing I could easily find about kh depleting is through old tank syndrome.

Does CO2 injection deplete kh drastically over a week since co2 is "stressing" the buffer?

I ask these questions since I have started injecting co2 again. Last time around I used a ph controller and drop checker. I became disgruntled the last time after my system failed. Cheap Chinese system.....

Anyway, My ph is about 7 now and the kh is about 6.5. This should give me a co2 reading of about 20ppm, which in my thoughts is a good starting point and a lot better than I had. If the kh would happen to lower, so would the co2.


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## TankAaron (Aug 8, 2014)

The following articles are very long, but will help answer your question.

AmericanAquariumProduts (Link thanks to Grizzle Fish)
Some of Grizzle Fish's notes
Seachem


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## anubias6439 (Sep 7, 2010)

WOW. Too much for my tired eyes tonight. Looks like some great stuff, I thank you for finding these articles. It should definitely "science" me up. Do people usually have to add extra kh, baking soda for example, throughout the week? I would assume yes under a low ph and hardness scenario. Neutral ph with medium hardness and an average kh of 6....... I don't know.


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## TankAaron (Aug 8, 2014)

I cannot add anything useful, unfortunately. You'll have to wait for someone who understands this. I am in a similar spot as you, in that I am still trying to understand this.

*IF* I remember correctly, KH is used, somehow, in a process that involves CO2. So, IF this is true, then yes, KH would slowly decrease. But doing weekly water changes helps stabilize that. If you are having major KH fluctuations, and you believe it is because of CO2, then there is probably something wrong, and it is not just the normal KH/CO2 synergy.

To help whoever will attempt to help you, you should post a few bits of information:

Tank size; If you happen to know actual amount of water in your system, it would help. Otherwise tank size alone is helpful.

Type of substrate.

Everything you dose, the measures of your doses, and how often you dose.

What kind of CO2 you're dosing; DIY? Pressurized?

Filtration: What kind? What media? Especially if you use chemical filtration.

Water flow/movement.

What do you use to measure what you dose? Test kits? Strips? Brands?

What plants do you have? Lights? Amount of hours you have the lights on.

These are some of the things that could affect CO2, and therefore KH.


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## anubias6439 (Sep 7, 2010)

it was more of a curiosity type post. I am on week 2 of pressurized CO2 injection. The tank has been fully planted since Saturday. I am seeing signs of good initial growth in the Blyxa japonica (in fact, its starting to redden and put out new leaves daily, at least it seems) and Micranthemum umbrosum (a little bit of pearling with some new green growth tips).

It is a 29 gallon with an emperor 280......... I know, not the best, but the ph has dropped from 7.4 to 7.0 with approximately 2.5 bps. Seems around the target mark anyway without having to shell out money for a canister filter I don't like. The canister might lower my consumption of CO2 by half, time will tell. I only run filter floss, NO carbon.

Substrate is a 80/20 mix of fluorite and pea gravel.

Lighting- 4 X 24 watt T5's (Geissman tubes, 2 6K's, 1 10K, and a Pink [roseate?] I believe). Lighting is staggered so all four lights are not on the length of the 10 hour photoperiod. I have 4 tubes on for 6 hours, may lower or raise that after observing plant/algae growth.

Fertilization is Seachem Comprehensive and Iron and Phosphourus from GLA. Nitrate is sufficient for the time being due to fish load (neons, epsei rasboras, bristlenose pleco)


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## Yo-han (Oct 15, 2010)

Some plants can use carbonate (KH) as a carbon source like other plants use CO2 as a carbon source. Plants always prefer CO2, so with CO2 injection they won't use the KH because it takes more energy.

So quick answer: with CO2 injection, plants will use less KH.

But then again, without CO2 a fully planted tank won't use more than 0,5 KH per week. So with regular (weekly) water changes it will never be a problem. Whenever you read about problems, people just don't change the water.


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