Does water change help raise KH and GH?

[martinmin]

The KH is low in my big tank, which causes low growth of plants, and the plants appear dull, dying, dry. My small tank looks much better and the KH is around 80, and the GH, pH is higher accordingly.

Does more frequent water change help  raise KH? 

  

[nabokovfan87]

Yes and no.

There are three things at play. Evaporation, Fertilization, and Dilution.

Evaporation. The water in the tank evaporates to the air and then you have the minerals in the tank compounding. In cooking this same mechanic is used to make sauces, reductions. This will raise the amount of minerals in the tank, creating what is called old tank syndrome.  There is also no real certainty to guarantee what is left in the tank because of the next issue.

Fertilization. Plants will pull minerals as they need them. This could be from the substrate. Especially an active substrate can pull those ions from the water column. If you have a planted tank, the best thing to realize is that this is constantly happening and that change in chemistry is going to impact a variety of things in the tank. There is such a way with something like a bog filter to pull so much of these things from the water that you are left with none over time. Eventually, that could theoretically happen as the plants and substrates filter those things.

Dilution. One of the common methods for a reef tank is to refill your tank with RODI water as to not impact any of their water chemistry. Doing  this ignores the tank itself using certain minerals. If we all had a reef, some method to test every single pertinent mineral in the water, then that would be the best way to determine input vs. output and how the water going in will dilute what is already there in terms of PPM.

The other side of the coin is that organics in the water use up KH ions. This means, let's say you add in your water and you see a KH drop after 24 hours. This makes sense in some situations. This is explained in this blog article pertaining to KH.

https://www.aquariumcoop.com/blogs/aquarium/ph-gh-kh

With those caveats aside, it is absolutely possible to use water changes to stabilize KH in your tank. Cory mentioned this in one of his older vlog videos where he was doing such a thing in one of his tanks. As long as the waste and organics in the tank don't use up the KH in the tap too quickly, yes, viable option.

On 6/10/2023 at 4:33 PM, martinmin said:

The KH is low in my big tank, which causes low growth of plants, and the plants appear dull, dying, dry. My small tank looks much better and the KH is around 80, and the GH, pH is higher accordingly.

In your big tank is there an active substrate?

[martinmin]

On 6/10/2023 at 4:40 PM, Pepere said:

It does if your water source has higher GH and KH.

 

my tap waters source is extremely soft and water district normally doses up to 2 degrees hardness.

For some reason though I tested the tap water today having 0 degrees each…

 

I dose Seachem Equilibrium and Alkalinity Buffer to raise both to 6 degrees.

How often do you dose Seachem Equilibrium? Do you need to dose constantly? 

On 6/10/2023 at 5:18 PM, nabokovfan87 said:

Yes and no.

There are three things at play. Evaporation, Fertilization, and Dilution.

Evaporation. The water in the tank evaporates to the air and then you have the minerals in the tank compounding. In cooking this same mechanic is used to make sauces, reductions. This will raise the amount of minerals in the tank, creating what is called old tank syndrome.  There is also no real certainty to guarantee what is left in the tank because of the next issue.

Fertilization. Plants will pull minerals as they need them. This could be from the substrate. Especially an active substrate can pull those ions from the water column. If you have a planted tank, the best thing to realize is that this is constantly happening and that change in chemistry is going to impact a variety of things in the tank. There is such a way with something like a bog filter to pull so much of these things from the water that you are left with none over time. Eventually, that could theoretically happen as the plants and substrates filter those things.

Dilution. One of the common methods for a reef tank is to refill your tank with RODI water as to not impact any of their water chemistry. Doing  this ignores the tank itself using certain minerals. If we all had a reef, some method to test every single pertinent mineral in the water, then that would be the best way to determine input vs. output and how the water going in will dilute what is already there in terms of PPM.

The other side of the coin is that organics in the water use up KH ions. This means, let's say you add in your water and you see a KH drop after 24 hours. This makes sense in some situations. This is explained in this blog article pertaining to KH.

https://www.aquariumcoop.com/blogs/aquarium/ph-gh-kh

With those caveats aside, it is absolutely possible to use water changes to stabilize KH in your tank. Cory mentioned this in one of his older vlog videos where he was doing such a thing in one of his tanks. As long as the waste and organics in the tank don't use up the KH in the tap too quickly, yes, viable option.

In your big tank is there an active substrate?

"In your big tank is there an active substrate": What do you mean by "active substrate"?

"it is absolutely possible to use water changes to stabilize KH in your tank. ": How long do I need to change water frequently to retain KH? 

[nabokovfan87]

On 6/10/2023 at 8:37 PM, martinmin said:

What do you mean by "active substrate"?

Stuff like aquasoil. The video above describes what "active" means and how that works. Briefly thought, it is a soil that has an ion exchange component. Common brands would be fluval stratum, tropica, ADA Amazonia, UNS Contrasoil, etc.

On 6/10/2023 at 8:37 PM, martinmin said:

How long do I need to change water frequently to retain KH? 

The second half of this video discusses a little bit of what you're dealing with.

The goal being that when you aren't using any buffers or additives, that your KH from the tap is what you see and test in the tank. You can do daily water changes if you really need to (30-50%) for most fish without any harm to the tank. For shrimp it is often cautioned to be a bit more careful with water changes.

With regards to buffers, I use the same stuff. I test, decide if I need to add some in. I also track before or after each water change to try to understand what is going on with my water. I ran into an issue where I stopped testing and my KH was about 2x what I expected. Strips told me one thing, liquid KH test and PH told me another. The main thing is to test if you're using buffers and having a lot helps. It's very straightforward. If your goal is 8 degrees of GH, and you're testing 6, you can add a little bit, give it a few days and add more. Same thing with KH, a little bit of buffer can keep the tank stable and it's not really complicated at all. I was adding a few scoops of 1/8 tsp per 5G per water change to get my KH stable. Based on that recent issue I would only do a single scoop per water change regardless and follow up with testing after 24 hours.

Edited June 12, 2023 by nabokovfan87
added video

[martinmin]

On 6/10/2023 at 10:47 PM, nabokovfan87 said:

Stuff like aquasoil. The video above describes what "active" means and how that works. Briefly thought, it is a soil that has an ion exchange component. Common brands would be fluval stratum, tropica, ADA Amazonia, UNS Contrasoil, etc.

The second half of this video discusses a little bit of what you're dealing with.

The goal being that when you aren't using any buffers or additives, that your KH from the tap is what you see and test in the tank. You can do daily water changes if you really need to (30-50%) for most fish without any harm to the tank. For shrimp it is often cautioned to be a bit more careful with water changes.

With regards to buffets, I use the same stuff. I test, decide if I need to add some in. I also track before or after each water change to try to understand what is going on with my water. I ran into an issue where I stopped testing and my KH was about 2x what I expected. Strips told me one thing, liquid KH test and PH told me another. The main thing is to test if you're using buffers and having a lot helps. It's very straightforward. If your goal is 8 degrees of GH, and you're testing 6, you can add a little bit, give it a few days and add more. Same thing with KH, a little bit of buffer can keep the tank stable and it's not really complicated at all. I was adding a few scoops of 1/8 tsp per 5G per water change to get my KH stable. Based on that recent issue I would only do a single scoop per water change regardless and follow up with testing after 24 hours.

I have an active substrate (black soil).

"Based on that recent issue I would only do a single scoop per water change regardless and follow up with testing after 24 hours." So whenever you do a water change, you add KH booster. How often do you do water change? If I do water change daily, it is going to be a big burden, both for labor and water cost. Who is going to do water change daily in reality in long term? 

[nabokovfan87]

On 6/10/2023 at 11:43 PM, martinmin said:

So whenever you do a water change, you add KH booster. How often do you do water change? If I do water change daily, it is going to be a big burden, both for labor and water cost. Who is going to do water change daily in reality in long term? 

Let's use a bit of a real world example to try to break down the method and some of the logic behind the decision tree.

Example:  KH in the tank is 20 ppm, KH from the tap is 80 ppm.  What we see in this case is a gradual decline of KH due to organics and waste building up and water changes being minimal (or not at all).  The hobbyist in this case wants to recover the KH a little bit, but you don't want to affect KH immediately due to how it impacts the PH of the tank.  This means you want to do so gradually over several days or 1-2 weeks.  First water change is 50%, KH goes from 20 up to 30.  Next time it goes from 30 up to 40, etc.  This is where you slowly see the organics removes via siphon and filter cleanings, improved maintenance.  Then you see the water chemistry itself recover.  This is the main method for recovering from Old Tank Syndrome. 

Example:  KH in the tank is 30 ppm, KH from the tap is 40 ppm.  There is a slight drop in KH here between the tank and the tap, but the fish in this tank need to have 7.4+ PH.  Due to the ppm of the KH being low, the water is going to have too low of a PH.  Ultimately, the only solution is to use a buffer like crushed coral or something like alkalinity buffer to raise the KH.  By raising the KH in the tank, you have the PH slowly rising as well.  For the same reason as mentioned above, you don't want to have the PH rise too swiftly so you would slowly add in your buffer until you reach the level you're happy with.  Crushed coral goes to the filter like a chemical media or into the substrate layer in the aquarium and slowly dissolves over time.  Using a powdered buffer it would be slowly adding the powder over several days or weeks.  Once your KH is at the right level in the aquarium, then you are going to be focused on maintenance of the KH water parameters.  You are preconditioning your water for water changes by adding the buffer, then using that for your water changes as you would normally.  Over time, in the case from my earlier post with evaporation, the KH will build up over time.  This just means monitoring things month to month (or week to week) to keep track of how the stability of the tank is doing.

Overall, water change schedule is up to you. It could be monthly, every few weeks, or weekly.  The dosing schedule is up to you and the livestock in the tank.  Some people dose in KH/GH just for the sake of plants to have the correct nutrient mix.  In terms of daily water changes, I would not be dosing buffers in daily.  They take time to dissolve and impact water parameters.  If you're in a situation where you need to perform more constant water changes, the main thing is to match the water from the tap.  Once you have things stabilized, then you can go back to using buffers and loosed schedule.  I was not preconditioning my water for water changes, but I was dosing it directly into the tank, minimally.  If I knew I needed say 5 scoops, I would dose in 2-3 scoops.  That is because my fish in my tank prefer lower PH, but I need to raise it enough to keep the tank from PH crashes.

[Lennie]

Do plants actually need kh? I think not. They usually just tolerate it in my experience.

I think your problem might be something different instead of low kh.

[martinmin]

The problem might be the fact that TDS from my tap water is 60. I have Flourish Advance Seachem and Green Brighty Neutral K, and Easy Green. Among these 3 liquid fertilizers, which one should I use to boost TDS, and KH and GH accordingly?

[Mmiller2001]

On 6/10/2023 at 5:33 PM, martinmin said:

The KH is low in my big tank, which causes low growth of plants, and the plants appear dull, dying, dry.

This is untrue, in fact the vast majority of plants available to us prefer 0 to low KH. If the TDS is 60, you are too low elsewhere. 

Here's a tank from GreggZ with 0KH and a pH of 4.85.

[martinmin]

On 6/11/2023 at 4:08 PM, Mmiller2001 said:

This is untrue, in fact the vast majority of plants available to us prefer 0 to low KH. If the TDS is 60, you are too low elsewhere. 

Here's a tank from GreggZ with 0KH and a pH of 4.85.

" If the TDS is 60, you are too low elsewhere." What do you mean? Can you elaborate on this?  My tap water TDS is 60. 

[Mmiller2001]

On 6/11/2023 at 5:44 PM, martinmin said:

" If the TDS is 60, you are too low elsewhere." What do you mean? Can you elaborate on this?  My tap water TDS is 60. 

Could be GH, either calcium or magnesium and low on NPK and/or micros. I would increase your fertilizer dosing and see what happens.

I would also test GH so the overall picture is clearer. But a tank TDS of 60 is real low. If you are dosing fertilizer, and reading 60 TDS, my suspicion is that GH is very low.

[martinmin]

On 6/11/2023 at 5:03 PM, Mmiller2001 said:

Could be GH, either calcium or magnesium and low on NPK and/or micros. I would increase your fertilizer dosing and see what happens.

I would also test GH so the overall picture is clearer. But a tank TDS of 60 is real low. If you are dosing fertilizer, and reading 60 TDS, my suspicion is that GH is very low.

60 is tap water. In the tank, TDS is about 90-100. 

It's new soil, so I haven't dosed fertilizer. I just started to dose liquid fertilizers today and hopefully it will increase TDS, because each new water change brings down TDS. GH is accordingly low and I have tested. I found TDS, GH, KH and pH are correlated. When one of them is high, others are high too. 

Does this mean I should slow down water change to retain TDS? 

Edited June 12, 2023 by martinmin

[nabokovfan87]

On 6/11/2023 at 3:09 PM, martinmin said:

Among these 3 liquid fertilizers, which one should I use to boost TDS, and KH and GH accordingly?

TDS has no bearing on KH and GH. Those are separate things. You can raise TDS and completely leave GH and KH unchanged.

You can raise GH or KH and in turn raise your TDS.

https://www.aquariumcoop.com/blogs/aquarium/ph-gh-kh

The above video and article should help to clarify any confusion.

[Mmiller2001]

On 6/11/2023 at 6:21 PM, martinmin said:

60 is tap water. In the tank, TDS is about 90-100. 

It's new soil, so I haven't dosed fertilizer. I just started to dose liquid fertilizers today and hopefully it will increase TDS, because each new water change brings down TDS. GH is accordingly low and I have tested. I found TDS, GH, KH and pH are correlated. When one of them is high, others are high too. 

Does this mean I should slow down water change to retain TDS? 

What is the GH? I would keep up on water changes and keep on dosing at the lower end and after the soil stops leeching excess ammonia ect, increase to normal dosing levels.

[martinmin]

On 6/11/2023 at 5:27 PM, Mmiller2001 said:

What is the GH? I would keep up on water changes and keep on dosing at the lower end and after the soil stops leeching excess ammonia ect, increase to normal dosing levels.

GH is under 100. The soil has stopped leeching excess ammonia. According to dosing instruction from Green Brighty Neutral K, it has to be dosed daily. That seems too much?  Easy Green is weekly based on recommendation. Flourish Advance Seachem doesn't say how to dose.   

On 6/11/2023 at 5:27 PM, Mmiller2001 said:

What is the GH? I would keep up on water changes and keep on dosing at the lower end and after the soil stops leeching excess ammonia ect, increase to normal dosing levels.

"I would keep up on water changes ". If new water washes away minerals, what's the purpose of water change? It's against the goal of raising TDS.

[Mmiller2001]

On 6/11/2023 at 6:43 PM, martinmin said:

GH is under 100. The soil has stopped leeching excess ammonia. According to dosing instruction from Green Brighty Neutral K, it has to be dosed daily. That seems too much?  Easy Green is weekly based on recommendation. Flourish Advance Seachem doesn't say how to dose.   

"I would keep up on water changes ". If new water washes away minerals, what's the purpose of water change? It's against the goal of raising TDS.

What's the GH of the tap water?

The purpose of water changes is to reduce build up of soluble and insoluble organics (there are no tests available at the hobby level for these) and to reduce and replenish nutrients. Only a TDS meter gives us information into organic build up.

I would do weekly water changes and replenish the fertilizer when you do. You should calculate the dose based on the actual water changed, not the tank volume. You can dose it all at once or divide the dose by however many days you would want to dose.

I personally front load all my Macros during my water change and dose my first day of micros. I then dose Micros 2 more days later in the week.

Front dosing an aquarium is more stable versus daily dosing after water changes.

[martinmin]

On 6/11/2023 at 6:03 PM, Mmiller2001 said:

What's the GH of the tap water?

The purpose of water changes is to reduce build up of soluble and insoluble organics (there are no tests available at the hobby level for these) and to reduce and replenish nutrients. Only a TDS meter gives us information into organic build up.

I would do weekly water changes and replenish the fertilizer when you do. You should calculate the dose based on the actual water changed, not the tank volume. You can dose it all at once or divide the dose by however many days you would want to dose.

I personally front load all my Macros during my water change and dose my first day of micros. I then dose Micros 2 more days later in the week.

Front dosing an aquarium is more stable versus daily dosing after water changes.

"What's the GH of the tap water?: GH： 25; KH: 45, PH:6.5

What about dose once if I plan to water change weekly after water change? This seems working for easy green's recommendation, but I still have Green Brighty Neutral K and it recommends dose daily. 

[Mmiller2001]

On 6/11/2023 at 7:11 PM, martinmin said:

"What's the GH of the tap water?: GH： 25; KH: 45, PH:6.5

What about dose once if I plan to water change weekly after water change? This seems working for easy green's recommendation, but I still have Green Brighty Neutral K and it recommends dose daily. 

If the tap water is 25ppm GH, how is the tank 100ppm GH? Are you dosing a GH product?

[martinmin]

On 6/11/2023 at 6:25 PM, Mmiller2001 said:

If the tap water is 25ppm GH, how is the tank 100ppm GH? Are you dosing a GH product?

No， because before water change, the TDS is 119, so a higher GH. It doesn't start from 0.

[Mmiller2001]

On 6/11/2023 at 8:24 PM, martinmin said:

No， because before water change, the TDS is 119, so a higher GH. It doesn't start from 0.

TDS is not GH. GH is a measure of calcium and magnesium in the water. GH is the hardness of the water.

Edited June 12, 2023 by Mmiller2001

[nabokovfan87]

On 6/11/2023 at 5:43 PM, martinmin said:

If new water washes away minerals, what's the purpose of water change? It's against the goal of raising TDS.

This all goes back to the CEC of the substrate.  An active substrate means it will pull minerals from the water.  The minerals you want it to pull is what essentially amounts to the recipe of equilibrium.  It will feed the plants the NPK they need at the substrate level.  You want to have a setup where GH > KH, preferable with GH being 2x your KH value.  This is not a hard and set rule, but it's something I've seen high end aquascapers follow to the letter.  There's 1,000,000 ways to run a planted tank.  I ran into a lot of issues when my GH dropped on me, and personally it is something I note now.

Alright.... let's break down the goal of what is going on.  I will start by reiterating that TDS has absolutely zero bearing on GH and KH.  GH and KH can impact your TDS, but TDS has nothing to do with what your GH and KH values are.  The video above by Cory goes into further detail on this topic.

1.  Tank is setup with initial parameters.
2.  Water changes introduce and or sustain those intial parameters, optimally they are equal.
3.  Your active substrate will absorb nutrients from the water due to CEC (ion exchange) which pull certain ions.  This affects your GH and KH of the water.
4.  To replenish those ions in the water and feed the soil you need to do water changes and/or dose in buffers.  The following schedule has been recommended and whatever substrate you purchased should have directions similar.
--->Week 1: Daily water changes
---> Week 2: 2-3 water changes
---> Week 3-4: 1 water change per week
---> Week 5-6: Normal maintenance

From a common soil substrate directions page:

Quote

How to use the product

Aquarium Soil ensures good and active growth from the beginning, and boosts the red plant shades.

It is a complete substrate, which can be used without any other types of bottom layer.

Aquarium Soil is further an active bottom layer that lowers the pH value and slightly affects the water chemistry.
We recommend that you change 25-50% of the water min. twice a week during the first 4 weeks after establishing the aquarium.

5.  Once the CEC of the substrate is used and filled, then you will see the tank stabilize.
Here is a chart from UNS showing the changes over time.

Edited June 12, 2023 by nabokovfan87

[martinmin]

On 6/11/2023 at 9:47 PM, nabokovfan87 said:

This all goes back to the CEC of the substrate.  An active substrate means it will pull minerals from the water.  The minerals you want it to pull is what essentially amounts to the recipe of equilibrium.  It will feed the plants the NPK they need at the substrate level.  You want to have a setup where GH > KH, preferable with GH being 2x your KH value.  This is not a hard and set rule, but it's something I've seen high end aquascapers follow to the letter.  There's 1,000,000 ways to run a planted tank.  I ran into a lot of issues when my GH dropped on me, and personally it is something I note now.

Alright.... let's break down the goal of what is going on.  I will start by reiterating that TDS has absolutely zero bearing on GH and KH.  GH and KH can impact your TDS, but TDS has nothing to do with what your GH and KH values are.  The video above by Cory goes into further detail on this topic.

1.  Tank is setup with initial parameters.
2.  Water changes introduce and or sustain those intial parameters, optimally they are equal.
3.  Your active substrate will absorb nutrients from the water due to CEC (ion exchange) which pull certain ions.  This affects your GH and KH of the water.
4.  To replenish those ions in the water and feed the soil you need to do water changes and/or dose in buffers.  The following schedule has been recommended and whatever substrate you purchased should have directions similar.
--->Week 1: Daily water changes
---> Week 2: 2-3 water changes
---> Week 3-4: 1 water change per week
---> Week 5-6: Normal maintenance

From a common soil substrate directions page:

5.  Once the CEC of the substrate is used and filled, then you will see the tank stabilize.
Here is a chart from UNS showing the changes over time.

For new tanks, for the 5-week-schedule, even if new water change brings down TDS, I still need to do water change by sticking to the schedule. Right? To raise TDS, in this 5-week-schedule, I can add liquid fertilizer to somehow compensate TDS loss cased by water change. Does this make sense?   

[nabokovfan87]

On 6/11/2023 at 11:53 PM, martinmin said:

For new tanks, for the 5-week-schedule, even if new water change brings down TDS, I still need to do water change by sticking to the schedule. Right?

You need to do water changes so that water in the tank is equivalent to the water you're putting into the tank.  TDS does not matter. What matters is your GH and KH values, specifically how those values compare from the tank vs. the tap where you perform your water changes.

Water changes replenish your minerals, via GH and KH.
 

On 6/11/2023 at 11:53 PM, martinmin said:

To raise TDS, in this 5-week-schedule, I can add liquid fertilizer to somehow compensate TDS loss cased by water change. Does this make sense?

Absolutely not.  Adding fertilizers at this point is a waste of fertilizers.  You're going to be doing water changes a bit too often.  Again, I think you're mixed up a little bit about the importance of GH and KH as opposed to the term "TDS".

TDS = Total Dissolved Solids.  This could literally be anything dissolved in water.  Salt, cleaner residue, waste, organics, fertilizers, minerals, etc.  Anything that dissolves in water adds to that TDS.  Please try to understand, you keep mentioning TDS.  We are trying to focus the conversation with regards to GH and KH only.  Those are the relevant items to your concern.
 

 

Here is another breakdown of what we are working with and the process, naturally, that you are experiencing.

https://tanninaquatics.com/blogs/the-tint-1/the-substrate-you-stick-with-the-idea-of-cation-exchange-capacity

Quote

What is "CEC?"

Cation Exchange Capacity (CEC) is the ability of a material to absorb positively-charged nutrient ions. This means the substrate will hold nutrients and make them available for the plant roots, and therefore, plant growth. CEC measures the amount of nutrients, more specifically, positivity changed ions, which a substrate can hold onto/store for future use by aquatic plants.

 

[nabokovfan87]

On 6/11/2023 at 5:21 PM, martinmin said:

60 is tap water. In the tank, TDS is about 90-100. 

I wanted to clarify why you are seeing what you are seeing in the tank.  You added soil.  Those fines, the organics from the soil increase TDS.  There is more "stuff" dissolved in the actual water in your tank.  What also happens is that the minerals in the water are absorbed into the substrate for later use by the plants.  That process.... that is the CEC we are discussing and trying to understand.  This is why the focus is on GH / KH and not compared to TDS.  By tracking what is really going on (GH and KH) then we can better understand if the soil is done charging and leeching.

  

On 6/11/2023 at 3:09 PM, martinmin said:

The problem might be the fact that TDS from my tap water is 60. I have Flourish Advance Seachem and Green Brighty Neutral K, and Easy Green. Among these 3 liquid fertilizers, which one should I use to boost TDS, and KH and GH accordingly?

This is where we are getting our wires crossed and there's some confusion.

TDS = "stuff" dissolved in the water. 

KH = buffer, directly tied to the PH stability of your water.  This is a broad term, but it refers to specific ions used in the water. 
Details for what this means will be in the Co-Op blog post link here:
https://www.aquariumcoop.com/blogs/aquarium/ph-gh-kh
 

Quote

KH (or Carbonate Hardness)

KH measures the amount of carbonates and bicarbonates in water, which affects the buffering capacity of the water. This means that KH helps neutralize acids and prevents your pH from changing too rapidly, which is useful because sudden pH crashes can cause health issues in your fish. Low KH means your water has less buffering capacity and the pH swings easily. High KH means your water has more buffering capacity and the pH level is hard to change.

Think of KH like a trash can. The higher the KH, the larger the trash can. If we overflow that trash can, then a pH crash occurs. Therefore, people with low KH in their tap water often use crushed coral to gradually raise the KH (or increase the size of their trash can) and prevent pH crashes.

GH = hardness of your water. 

Quote

GH (or General Hardness)

GH measures the amount of calcium and magnesium ions in the water – in other words, how hard or soft your water is. It’s one of the easiest ways to measure if your aquarium water has enough salts and minerals that are essential for healthy biological functions, such as fish muscle and bone development, shrimp molting, snail shell development, and plant growth.

 

So in a very simplified example:

In your tank, water is increasing in TDS because of the organics in the soil dissolving in the water.  However, the water itself is Decreasing in GH and KH because those minerals are being absorbed into the substrate via the CEC process.  Water changes help to remove the excess organics in the water from the new soil.  After a few weeks this is not required.  The tank will stabilize.  Water changes will also replenish the GH and KH of the water so that eventually those values will also stabilize.  Once that process is complete, then you would treat the tank as "cycled" and you can fine tune things like your fertilizer dosing.

Edited June 12, 2023 by nabokovfan87

[martinmin]

On 6/12/2023 at 12:53 AM, nabokovfan87 said:

I wanted to clarify why you are seeing what you are seeing in the tank.  You added soil.  Those fines, the organics from the soil increase TDS.  There is more "stuff" dissolved in the actual water in your tank.  What also happens is that the minerals in the water are absorbed into the substrate for later use by the plants.  That process.... that is the CEC we are discussing and trying to understand.  This is why the focus is on GH / KH and not compared to TDS.  By tracking what is really going on (GH and KH) then we can better understand if the soil is done charging and leeching.

  

This is where we are getting our wires crossed and there's some confusion.

TDS = "stuff" dissolved in the water. 

KH = buffer, directly tied to the PH stability of your water.  This is a broad term, but it refers to specific ions used in the water. 
Details for what this means will be in the Co-Op blog post link here:
https://www.aquariumcoop.com/blogs/aquarium/ph-gh-kh
 

GH = hardness of your water. 

 

So in a very simplified example:

In your tank, water is increasing in TDS because of the organics in the soil dissolving in the water.  However, the water itself is Decreasing in GH and KH because those minerals are being absorbed into the substrate via the CEC process.  Water changes help to remove the excess organics in the water from the new soil.  After a few weeks this is not required.  The tank will stabilize.  Water changes will also replenish the GH and KH of the water so that eventually those values will also stabilize.  Once that process is complete, then you would treat the tank as "cycled" and you can fine tune things like your fertilizer dosing.

The reason I want to monitor TDS is that:

1) It's simpler to monitor the water parameter than test strip and cost nothing, though I do use test strip a lot. Hopefully, a simple TDS reading can tell most if not all about gh, kh and ph.

2) TDS contains at least magnesium and calcium and that's why I thought TDS is also an indication of at GH. And by using test strip, I often found that when GH is high, KH is high too.

The problem is, if I don't add liquid fertilizer after water change, given the low TDS, GH and KH from my tap water, how to raise them in my tank?