# A GH KH Crushed Coral Experiment



## Jarrod987 (Aug 18, 2015)

I was curious if using more or less Crushed Coral (Actually using oyster grit in this experiment) would have an effect on the equilibrium over time. The old advice was always to use "one hand full".

I used 2 glasses and put 1 spoon of rinsed Oyster Grit in one and 4 Spoons in the other. I added RODI water. LEt them soak for 1 hour.

I will refer to the 1 spoon glass as glass 1 and the 4 spoon glass as glass 2.
GH and KH are reported in DKH with API kit and pH was read with PHEP 5 from Hanna Instruments.

After 1 hour
Glass 1 pH 7.7 GH 3 KH 2
Glass 2 pH 8.2 GH 5 KH 3

After 26 Hours
Glass 1 pH 7.5 GH 4 KH 3
Glass 2 pH 7.9 GH 6 KH 4.75

After 50 hours (Added top off RODI water)
Glass 1 pH 7.8 GH 5 KH 4
Glass 2 pH 8.0 GH 5 KH 4

After 165 hours
Glass 1 pH 7.7 GH 6 KH 5.5
Glass 2 pH 8.0 GH 7 KH 5.5

Conclusion:
The tests are not super accurate so this is very rough data. It appears that more CC will result in the water buffering faster which is very good. Especially if plants are eating your GH very fast or Bacterial acidification is an issue. However, it appears the stabilization of the parameters is about the same no matter how much is use.


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## Diana K (Dec 20, 2007)

This is a factor of equilibrium. 
Only so much of these minerals will dissolve in the water. As the concentration of these minerals rise, less will dissolve. It does not matter if you start with a lot or a little, eventually there will be a certain level of minerals in the water and no more will dissolve out of the oyster shell. 

This is also a factor of surface area of the particles. When you add more of the same size particles (glass 2) you have more surface area. This means more contact with the water, so more minerals can get into the water when you first start the experiment.

It also relates to the pH of the water. When the water starts off more acidic, more of the minerals will dissolve, and this raises the pH, so you may get a fast start, but it will still reach the same equilibrium point of GH, KH and pH. 

Net result:
With more surface area, the minerals enter the water faster. (Glass 2 has a faster rise in GH, KH and pH). 
But this means it reaches equilibrium sooner, so less minerals enter the water as the experiment continues. (Values even out over a day or two).

Given the imprecise measurements of hobby level test kits, I think you have reached the right conclusion: 
If you want fast results (perhaps during water prep ahead of a water change) then use more, and I would suggest an improved water flow through the oyster shell, and the finest particles you can find. Grit for Budgies will be better than the oyster shell sold for chickens. Oyster flour may give the fastest results, but I want to see if it clouds the water. (just got some a few days ago to test)

If you want something in the filter that will stabilize the GH, KH, pH over time, then a smaller volume or coarser material is just as effective as a larger volume or finer material (greater surface area). This assumes the water that was added to the tank was already prepped to the right parameters, and all you are expecting of the material in the filter is to replace what the plants and other biological processes are removing from the water. 

You would get similar results, though perhaps slightly different levels, with similar materials:
Aragonite
Coral sand
Limestone sand or gravel
Dolomite sand or gravel
Sea shells
Texas Holey Rock and other limestone related materials

There are other materials which are basically calcium or magnesium carbonates, and they dissolve at different rates, and have minor variations in mineral levels. The essential chemistry concepts do not change, though. When there is a certain amount of something in the water, no more of that thing will dissolve in the water. 

In aquariums for rift lake Cichlids, for example, coral sand substrate, and Texas holey rock will only raise the levels to a certain point, then they stop dissolving. That level happens to be similar to the natural levels in these lakes, because there are a lot of limestone formations around and in the lakes.


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## niko (Jan 28, 2004)

You can do that.

Or you can use Magnesium Carbonate and Calcium Carbonate to adjust GH and KH. Both of them dissolve fully in about 2-3 hours in slightly acidic water. But nobody uses them because people just love to add extra stuff to their water (Mg and Ca Chloride).

With the Mg and Ca Carbonates adjusting the GH and KH is extremely precise. But what you will find is that depending on your plants' condition they may suck Mg like crazy or not at all. Also you will see how hard it is to maintain a 4:1 ratio of Ca:Mg. You will need good tests too, not cheapo aquarium crap tests.

So you can make this as precise as you want or as easy as you want with coral. I'd go for easy if it works.


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## Silvering (Jun 10, 2011)

I had some aragonite left over from my cichlid tank, and added some to my canister filter on my planted tank in a filter bag. My crypt spiralis was suffering excessive curling before, but now it's back to growing its leaves nice and straight.


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## Jarrod987 (Aug 18, 2015)

Isn't oyster grit exactly those? You must mean a powder?


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## Diana K (Dec 20, 2007)

These materials are often available in different material sizes, and you can certainly adjust the volume to do what you want. By keeping the material of choice in a mesh bag you can easily remove it from the filter it if it doing more than you want. 

I usually prep water for hard water fish using baking soda or potassium bicarbonate for KH and Seachem Equilibrium for GH. Then I keep coral sand or dolomite in the tank as substrate. Since I have prepped the water before hand, there is no shock to the fish when I change the water, and the substrate only dissolves very slowly, acting to stabilize the water parameters rather than actually changing them as would happen if I did a water change using soft tap water.


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## Jarrod987 (Aug 18, 2015)

Diana K said:


> These materials are often available in different material sizes, and you can certainly adjust the volume to do what you want. By keeping the material of choice in a mesh bag you can easily remove it from the filter it if it doing more than you want.
> 
> I usually prep water for hard water fish using baking soda or potassium bicarbonate for KH and Seachem Equilibrium for GH. Then I keep coral sand or dolomite in the tank as substrate. Since I have prepped the water before hand, there is no shock to the fish when I change the water, and the substrate only dissolves very slowly, acting to stabilize the water parameters rather than actually changing them as would happen if I did a water change using soft tap water.


Sounds pretty much like what I was planning. I already bought the Equilibrium but Seachem told me it wasn't designed for plants and the chloride could cause problems in some species so I backed off it. They told me there new line has a GH booster made for plants. I haven't got around to it yet.


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## Diana K (Dec 20, 2007)

Equilibrium is just fine for plants. 

From Seachem web site:
"Derived from: potassium sulfate, calcium sulfate, magnesium sulfate, ferrous sulfate, manganese sulfate."

No chlorides.


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## Jarrod987 (Aug 18, 2015)

Diana K said:


> Equilibrium is just fine for plants.
> 
> From Seachem web site:
> "Derived from: potassium sulfate, calcium sulfate, magnesium sulfate, ferrous sulfate, manganese sulfate."
> ...


I made a mistake. Replenish is what I bought. Equilibrium is the one they told me to use. Sorry about that. I get mixed up sometimes.


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## Jarrod987 (Aug 18, 2015)

Update:
I found my old LaMotte Ca test kit today. Works with fresh or salt water. Reagent is old so probably no good but it is dry tablet so those can last a long time. Anyways with API reporting KH of 8 dKH LaMotte reports a Ca Hardness of 100 ppm. It is a tritration test.


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## Jessy2363 (Aug 27, 2015)

Hi people, first post at this forum. I have a low KH problem therefore PH crashes are so easily done I am to afraid to turn on my new Co2 pressurised system as I had a PH crash and almost killed my fish. Now I am reading lots about buffering KH. I want a DIY method. My options are from what I've read. Potassium Bicarbonate or Calcium Carbonate. (I am not keen on sodium bicarbonate). Now I am leaning towards potassium Bicarbonate. However Is Calcium Carbonate more stable? I know that oyster shells are primarily made up of this ingredients. Thing is, I read a few posts and information online that Calcium Carbonate starts to become soluble at a PH lower than 6.3 creating more Co2 (somehow). Putting the fish at risk if the PH does get that low. Therefore would it be dangerous to have oyster shells or use Calcium Carbonate as a KH buffer in the tank? There is no guarantee my PH won't go below 6.3 one day!!? Especially considering my already low KH tap water. Or can the same thing happen with any bicarbonates? (not just Calcium carbonte) Please help me as I have been googling for hours to figure out which one to choose and its driving me a bit nuts considering my chemistry knowledge is not all that. I have access to all minerals/salts etc. Thanks. Jess


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## Jarrod987 (Aug 18, 2015)

I am using Oyster grit from the feed store right now. It is calcium carbonate just like crushed coral but much cheaper. Will provide not just calcium and carbonate but also magnesium to your tank. It does not provide co2. it does provide alkalinity which some plants can use instead of co2 but there is no danger of suffocation from that. The way it works is that the lower your pH gets the more acidic your water becomes. The more acidic the faster the oyster grit (or crushed coral) will dissolve and the faster that will push your GH (Calcium and magnesium) and KH(alkalinity also called carbonate) back up. The faster KH goes up the faster pH goes up. So Oyster grit makes pH go up and Co2 Makes it go down. They reach a stable equilibrium in theory. In reality there are minor deviations in pH over the day but not a huge deal. That is normal. Takes up to 2 weeks for this equilibrium to be reached. Just go slow with the co2. Tiny adjustments , wait a day, figure out your co2 ppm and monitor your ph etc.


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