# Can plants reduce kh?



## kidgrave (Feb 4, 2014)

Once in a while, I watch videos from Dustin's Fish Tanks on Youtube; however, a lot of the information that he gives and talks about seems confusing, and sometimes well not explained. I read online where he talked about using crushed coral in the substrate to prevent the kh from dropping. He was talking about how plants could reduce the carbonate hardness. His fish tanks already have a high ph, so I don't understand why he would use crushed coral, which will raise the ph and kh. 

Can someone please explain to me under what circumstances the kh would drop, or about the water becoming acidic?

I hope I am not asking a dumb question, but I want to make sure that I learn something new everyday out of this hobby. :red_mouth


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## Solcielo lawrencia (Dec 30, 2013)

Yes, plants can take up carbonates for the carbon source. Water can become acidic due to various biological factors which release acids.

PH is just the measure of acidity. It tells us nothing about hardness. E.g. water immediately out of my tap is pH=8.5-9 and kH=2-3 but it is very soft with very little Ca or Mg. Thus, my water isn't good for hard-water fish. Ca and Mg must be added.


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## kidgrave (Feb 4, 2014)

Solcielo lawrencia said:


> Yes, plants can take up carbonates for the carbon source. Water can become acidic due to various biological factors which release acids.
> 
> PH is just the measure of acidity. It tells us nothing about hardness. E.g. water immediately out of my tap is pH=8.5-9 and kH=2-3 but it is very soft with very little Ca or Mg. Thus, my water isn't good for hard-water fish. Ca and Mg must be added.


Thanks for your reply. Under what circumstances do plants use Kh as a carbon source? What can be done to prevent the water from becoming acidic?

Do you dose Seachem Equilibrium to raise your Ca and Mg?


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## Solcielo lawrencia (Dec 30, 2013)

As far as I know, when CO2 runs out, some plants can use CO3. I don't know if all plants can do this. It's metabolically expensive to do so and is not the preferred carbon source.

I don't add Equilibrium (it's expensive) but do add Ca, Mg, and K in the forms of CaSO4, MgSO4, and K2SO4. These are the actual ingredients of Equilibrium.


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## JoeRoun (Dec 21, 2009)

*Hydrogen Says I Lost My Electron, I'm Positive*

Beyond certain plants reducing carbonate hardness (KH) when striving to replace CO2, which would generally be minor, biological processes tend to be acidic. Remember that our little aquatic worlds are obviously aqueous. 

We tend to forget that water itself dissociates and ends up having a Hydrogen to give. So without getting too technical (practical chemistry) there is a tendency toward lower pH. 

KH provides resistance to change in pH, we call that buffering. If you have fish maybe African Cichlids, perhaps from Lake Tanganyika, you may wish to keep the pH above 8.8 perhaps even 9.2, that actually requires some work, hence the crushed coral.

Most of time we in the planted tank end of things tend to prefer “softer” water and often with the addition of CO2 and such keep the water toward neutral or even a little acidic. Turns out most of our plants prefer that. It also turns out our critters are less likely to die from Ammonia toxicity.

I am with Solcielo lawrencia, I don't add Equilibrium (also because it’s expensive) but do add Ca, Mg, and K in the forms of CaSO4, MgSO4, and K2SO4.

Joe
FRTB


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## kidgrave (Feb 4, 2014)

Solcielo lawrencia said:


> Yes, plants can take up carbonates for the carbon source. Water can become acidic due to various biological factors which release acids.
> 
> PH is just the measure of acidity. It tells us nothing about hardness. E.g. water immediately out of my tap is pH=8.5-9 and kH=2-3 but it is very soft with very little Ca or Mg. Thus, my water isn't good for hard-water fish. Ca and Mg must be added.


What's the GH of your water? My water Gh is at 16. Is that Gh unhealthy for Neon Tetras? Does Gh mostly matter when it comes to breeding fish?

Bump:


JoeRoun said:


> Beyond certain plants reducing carbonate hardness (KH) when striving to replace CO2, which would generally be minor, biological processes tend to be acidic. Remember that our little aquatic worlds are obviously aqueous.
> 
> We tend to forget that water itself dissociates and ends up having a Hydrogen to give. So without getting too technical (practical chemistry) there is a tendency toward lower pH.
> 
> ...


Hi, thanks for your reply. I got a question for you. Is dosing PPS Pro a bad idea on hard water like mine? The GH of my water is 16. The PPS Pro solution does have MgS04, and K2S04.


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## Diana (Jan 14, 2010)

Get each element separately, so that you add just what you want. 

What units are you using when you say the GH is 16. 16 whats? 
German degrees of hardness? That is hard water!
Parts per million? That is soft water. 
No matter what you do, always show the units! 

If you are using a pre-blended mix of what someone else thinks is the right fertilizers, how can you take out the stuff you do not need? 
Hard water (high GH) usually has plenty of both Ca and Mg for the plants and fish (Yes, the fish use these minerals from the water, too), so there is no point in adding more. 
Also, if you do have soft water, and want to raise the GH you need to know if there is an imbalance between the Ca and Mg, and add the right material, the one that is actually lacking in the tank. Not just add Mg to make the GH test read the right number. So, I am against any manufacturer creating one blend and saying it works for all, when it is so obviously wrong. 

Some fish will keep on taking in the minerals and storing them in their body until they die from too much of something. Keeping soft water fish in high GH water can lead to this sort of problem. Cardinal Tetras are known for accumulating calcium like this. 

To keep soft water fish when you have hard water:
Blend your hard water with distilled or reverse osmosis water until the GH is in the right range for the fish. If you think there is a problem with the Ca:Mg ratio, then correct it with the right material. Plants use Ca and Mg in a ratio of about 4:1. The water does not have to be exactly that, but sort of close is a reasonable target. 
Then check the KH. This is carbonates and bicarbonates. The KH should be fairly close to the GH. 
Once these 2 values are right the pH ought to be in the correct range for the fish. The pH is less important, and if it is not quite right, most fish will do just fine, as long as the mineral levels are right. 

Some tap water is very skewed. Lots of GH and low KH or the opposite: GH is low, but the KH is sky high. 
This is difficult to deal with, though the concept is the same:
Dilute the minerals until the one that is way too high is right. Then add the right materials to bring the low value into the right range. 

Example: 
Tap GH 1 degree, KH 10 degrees. 
So, dilute this with RO @ 50/50 RO:Tap. 
Net result GH is .5 degrees, and KH is 5 degrees. PH may have dropped. 
So add some GH booster until the GH is at least 3 degrees. 
If the pH is still way up, and you want it lower, then try filtering the water through peat moss.


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## kidgrave (Feb 4, 2014)

Diana said:


> Get each element separately, so that you add just what you want.
> 
> What units are you using when you say the GH is 16. 16 whats?
> German degrees of hardness? That is hard water!
> ...


I am using an API GH & KH General and Carbonate Hardness Test Kit. When I was testing for the GH, it took 16 drops to change the color. I think this would be german degrees. 

My tank is 10 gallons; therefore, I don't mind using distilled water or RO to lower the hardness. 

I have a question about RO units because I want to soften up my water, and also because my family wants to purchase one. When I use RO water, what is it that I have to adjust or tweak? I hope I am not asking anything ignorant here, but does RO water have a ph? Does R0 water have a GH and Kh of 0? I just want to know what I need to adjust once I do buy an RO unit.

I want to make sure that I understand what you explain to me. Let's say I need to replace evaporated water, is it best to use distilled water? I heard that using tap water to replace evaporated water could increase the salts. 

I can't wait to get my RO unit. Let me know if there is any brand that I should purchase.


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