What Is A Healthy Level Of Kh?

Good morning everyone,

So from what I read, I get that KH is very important to ensure a good water stability (against PH swings). Problem seems to be that my KH is etremely low (1 or 2 - water changes color after the 2nd drop). GH on the otherside is pretty high, 13. The pH has for now stayed constant at 6.5.

Is this KH good enough, or should I increase it somehow? If yes, how do I do that?

Tank info: 180L, planted, fish&shrimp tank.

 

HI happah, I'd recommend buffering it up to 6-7 using a bag of crushed coral.

 

What is the procedure? Place some crushed coral and remove it once the level hits 6-7? or leave it there permanently

 

Your KH does seem to be on the low side if it's 2. Most people want a minimum of 4.

To raise KH without raising PH you'd add some Potassium carbonate (K2CO3)
To raise KH and PH you'd add some Sodium bicarbonate (NaHCO3) [baking soda]
just don't use soda ash which will raise your GH as well if you don't want it higher.

 

When using crushed coral to raise your KH, you leave it permanently.

 

I have to have crushed coral in all my tanks. My tap water’s pH is 7.8, but the kH is very low. Before I used crushed coral, the pH in my tanks would eventually get so low that my cycle would crash. I just put a media bag full of crushed coral in each of my filters and voilà! The pH is always stable and the tanks stay cycled!

 

Sorry for asking so many questions; will the crushed coral also increase my GH? It is already very high as it is.

Also, if I add some in my filter - at what intervals does it need to be changed?

On the berlin water website it says that tap water should have 6-8 KH, but in the 3 instances I measured it in my aquarium, it always comes down to 2.
EDIT: So I measured the tap water - it comes out at 7KH, but in the aquarium it stays at 2KH. Why is this happening?

 

To raise KH without raising you'd add some Potassium carbonate (K2CO3)

Any carbonate salt, including potassium carbonate, will result in a corresponding increase in pH as a result of an increase in KH.

So I measured the tap water - it comes out at 7KH, but in the aquarium it stays at 2KH. Why is this happening?

Many chemical reactions that take place in the tank (e.g. the oxidation of ammonia to nitrite) steadily acidifies tank water and lowers KH. The solution is to do larger and more frequent water changes to maintain a stable KH/pH.

I'll offer a different perspective: I think a low (even 0) KH is fine. I've read of many Discus owners/breeders who raise their stock in 0 KH water. The more important attribute is, I think, KH stability.

 

Any carbonate salt, including potassium carbonate, will result in a corresponding increase in pH as a result of an increase in KH.

The above quote is incorrect. It doesn't raise pH because that compound doesn't have a hydrogen atom therefore when buffering you don't get a free Hydrogen atom which can bind to increase HO count (pH).

My reference was KH - The Free Freshwater and Saltwater Aquarium Encyclopedia Anyone Can Edit - The Aquarium WikI if it's wrong we need to fix it but I believe it is correct because it unlike the other compounds doesn't have a hydrogen atom.

 

I'll offer a different perspective: I think a low (even 0) KH is fine. I've read of many Discus owners/breeders who raise their stock in 0 KH water. The more important attribute is, I think, KH stability.

I do plan to also have lots of shrimp in the aquarium, and set my eyes on some Blue Tiger Shrimp & Red Tiger. From what I understand, they would prefer a 4-5 KH level, so this is why I am thinking about how to raise the KH level.

I am worried though about causing sudden pH swings when adding K2CO3. My water is slightly acidic (6.5) and from what I understand this causes some pH spikes when adding any carbonate.

 

I do plan to also have lots of shrimp in the aquarium, and set my eyes on some Blue Tiger Shrimp & Red Tiger. From what I understand, they would prefer a 4-5 KH level, so this is why I am thinking about how to raise the KH level.

I am worried though about causing sudden pH swings when adding K2CO3. My water is slightly acidic (6.5) and from what I understand this causes some pH spikes when adding any carbonate.

I doubled checked what the wikI site states. We'd need a chemist in the house to certify it for sure but I believe K2CO3 would not increase your pH as the wikI site states. Unfortunately it's a food additive and I don't happen to have any of it or I would test it myself. What the wikI states makes sense. Most buffering compounds have an H atom in them which could combine with a free O ionto make HO- (base). K2CO3 doesn't have it and therefore can not raise pH.

 

What the wikI states makes sense. Most buffering compounds have an H atom in them which could combine with a free O ionto make HO- (base). K2CO3 doesn't have it and therefore can not raise pH.

The carbonate ions formed by the dissolution of K2CO3 are hydrolysed to form hydroxide ions:

(CO3)2- + 2H2O => H2CO3 + 2OH-

It's the same reaction by which calcium carbonate (crushed coral) raises KH and pH.

]This is a thread on Fishlore from 2 years ago from a person who followed theaquariumwiki's recommendation on using K2CO3 to raise KH without raising pH. They tested the after effects and recorded a rise in pH from 7.4 to 8.4 in a 10 gallon tank using a 1/4 teaspoon of K2CO3.

 

The carbonate ions formed by the dissolution of K2CO3 are hydrolysed to form hydroxide ions:

(CO3)2- + 2H2O => H2CO3 + 2OH-

It's the same reaction by which calcium carbonate (crushed coral) raises KH and pH.

from a person who followed theaquariumwiki's recommendation on using K2CO3 to raise KH without raising pH. They tested the after effects and recorded a rise in pH from 7.4 to 8.4 in a 10 gallon tank using a 1/4 teaspoon of K2CO3.

Yep Potassium carbonate, when mixed with listed as strongly alkaline pH of 11.6 with water it appears.

 

So basically, there's no way I increase the KH a couple of degrees without changing the pH. Now I wouldn't have a problem if the pH were to stay at 7.5 for example (although I hear shrimp like it acidic?), but dosing a carbonate would basically mean swinging the pH between the value it is now at (6.5) and some higher value; I add carbonate, pH goes up; Carbonate get used up, pH goes down. Seems like a dangerous game to play.

I'll try some crushed coral in larger pieces droped in the Aquarium; I'm thinking that if it's slowly dissolving, it would mean a steadier source of carbonate, with little swings, and thus a bit more stability/

 

When I'm mixing something around for a situation like this I use a separate tank / container anything. That way if I make a mistake I can go back instead of using the target tank as the first mixing bowl and I can move the numbers in small amounts a little on each water change. I can't comment anything on the shrimp part or how long crushed coral takes to work.

 

Seems like a dangerous game to play.

I think it's important to note that when issues of pH fluctuations are being discussed, the issue of concern are KH fluctuations. Large, sudden, frequent fluctuations in KH (which leads to corresponding changes in pH) disrupts the osmoregulation process in fish and invertebrates, and negatively impacts numerous physiological processes.

As an example: CO2 lowers the pH of water, but it otherwise exerts no effect on the level of KH. This is why planted tank aquarists are able to subject their tanks (and the fish therein) to daily fluctuations of 1-1.5 pH increases/decreases with no ill effects.

Why is it the case that we refer to pH when the underlying factor is KH? Because pH is easier to measure than KH.

All tap water (unless it's RO filtered) has some degree of dissolved carbonates, and this gets gradually used up. Most people find that their tank water at the end of the week is more acidic than their tap water, and this is just the outcome of numerous chemical processes in the tank. This gradual decrease in KH (and pH) over the span of a week really poses no issues for aquatic life.

In addition, I really wouldn't worry about whether you're adding calcium carbonate, sodium bicarbonate or potassium carbonate: they'll all exert the same effect on KH (and correspondingly, pH). It's more important to maintain consistency in how much you dose and when you dose. I've read of aquarists who don't like the crushed coral method as it's difficult to regulate the rate of dissolution (which varies from coral to coral) as it makes it hard to target a specific ppm: they often prefer dosing a specific quantity of baking soda during water changes to target their desired KH.

 

I only use a few small pieces of oyster shell in my filter, so my KH is usually kept around 2 or 3 for my acidic water fish.

 

Hm, so it is actualy safer to dose a carbonate. May I ask for some advice regarding the dosing quantity of baking soda, in an approx 130l of water, to raise KH from 2 to 4?

Also one more question; I see you mentioned the dosing being done with the WC; would it not make more sense to do it a couple of days after, since the tap water already comes with 6-7KH ?

 

A 2 dKH increase can be achieved with 7,800 mg of NaHCO3.

That's approximately 1.5 level teaspoons of NaHCO3 (baking soda). I'd recommend using 1 quarter teaspoon per day and measuring an hour after each dose (allow time for circulation). Stop when you reach your desired KH.

Regarding the water change, I should've clarified and meant "water changes with RO water": one needs to adjust the GH/KH/TDS (and specific gravity for marine tanks) for RO water before adding it to the tank, otherwise it causes osmotic shock.