Is Carbonate Hardness (KH) Necessary In CO2-Injected Tanks? - The Planted Tank Forum
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post #1 of 4 (permalink) Old 02-01-2016, 02:17 AM Thread Starter
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Is Carbonate Hardness (KH) Necessary In CO2-Injected Tanks?

I am venturing back into the realm of injecting CO2 gas into my tank. As I am doing research, I am seeing references where it is no longer necessary to add any additional buffering agent. Is this true?

I keep a bunch of dwarf shrimps, hardy and sensitive species. I use RO water and reconstitute with Salty Shrimp's (Bee Shrimp) Mineral GH+. What exactly is in this product is beyond me. I don't see the ingredients listed on the label. It simply states that it "raises the total hardness (dH) without significantly influencing the carbonate hardness (KH)." Well, I can safely assume that it contains calcium (Ca) since it is a bee shrimp-specific product. Whether or not it has magnesium or whether the Ca is in SO4 or CO3 form is not specified. Coupled with the fact that I use an active substrate, I don't really know what cumulative effect(s) do these two products have on my KH.

So as I begin to add CO2 gas, do I need to worry about the pH swings or shall I count on my substrate to provide all the "biological buffers" that my tank need?

I like a minimalistic and chilled approach to this hobby so I would like to avoid fiddling with test kits if at all possible.
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post #2 of 4 (permalink) Old 02-01-2016, 02:47 AM
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What is the KH of the water before you add the water to the tank?
What is the KH of the water after it has been in the tank for a few days? IF the KH drops, then the substrate might be removing the carbonates. This could complicate the problem.

If the KH is high enough (it does not have to be very high, just not zero) then the pH will vary according to how much CO2 you are adding.
Test the pH in the tank without CO2.
Start the CO2 and allow it to run long enough to be well circulated through the tank. Test the pH.

If the pH changes by 1 unit, then you have 30ppm CO2 in the tank. This is a really good amount for the plants.
But if this low pH is lower than the shrimp want then you might want to start with the pH higher so that when it drops it does not get quite so low.

To make the pH start out a bit higher, add carbonates. Keep the pH at the upper end of the acceptable range for the livestock.
Then add CO2, and the pH ought to still be within the acceptable range, but now it may be at the lower end of this range.

The most common material added to a tank to raise the KH is sodium bicarbonate. Baking soda.
But if the shrimp do not like sodium, you may want to try potassium bicarbonate.
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post #3 of 4 (permalink) Old 02-01-2016, 03:13 AM Thread Starter
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I use RO water, so 0 degrees of KH. I also use an active substrate that also affects my KH; although, in what way, I have no idea.

Years ago, I injected CO2 and cared little for the fauna so I adopted an Estimative Index (EI) style of keeping my plants: I assume my tap water has nothing and proceeded to add KH, GH and nutrients as I observe plant health. Everything was spectacular! Now that I house and develop an affinity for finicky shrimps/fish, I have to find some kind of compromise between the fauna and flora. I can't just EI my RO water and have the annoying fauna happy. But if I give them the 0 KH they so love, I fear that I may gas the stupid little things to death.

So my dilemma: I rather not add any carbonate if KH is no longer important: fauna likes it and I have one less thing to add. But if I have to add KH, then what is that pesky active substrate going to do to all that lovely CO3?
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post #4 of 4 (permalink) Old 02-01-2016, 04:13 AM
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Most tap water gets KH from calcium carbonate in the water, but not all. For those whose tap water is like that little attention needs to be given to KH. But, if you strip out all of the minerals in the water, you need to put most of them back for both the plants and the fauna. As I recall, shrimp don't do well with lots of CO2 in the water, so if you want to keep shrimp you should probably not be using more than low medium light, so you won't run into algae problems from not using a lot of CO2. Very few fish, if any, will be bothered by the amount of CO2 needed by the plants. But, if you add CO2, and have an extremely low KH, the pH of the water will drop enough to possibly be a problem. However, as I recall, the lowest you can drive the pH with CO2 is around 5.5, and I don't think that bothers the vast majority of fish. Again, however, the very low KH is another matter, and I do think that can be a problem for several types of fish. If I have added enough confusion I will stop now

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