Lowering GH without affecting PH and KH

I have a 30 littre betta tank (Almost 8 gallon), where the GH is way too high to the point my shrimps are dying in their molts.

My KH is around 6°d and my PH is around 6,8. But GH is >21°d, so as in it's completely bad. The rest are 0 or low enough to be safe.

I've been adding easybalance by tetra every water change. I even did 50% water change and added distilled water instead of our usual tap water. But I don't see any improvements.

So I've been researching what I can do, like getting a RO water. But I've checked the price and that might be an overkill to get it. Getting some alder cones or peat moss, but all of them lower the existing PH. If I add these, my PH will become dangerously acidic.

Currently I don't have a fish as I had to euthanize him due life quality being ruined. I have only few shrimps that somehow still manage to survive and a nitre zebra snail.
Plants are Anubia Nana, which i'm going to remove as it's growing black algae and it seems to be spreading to other leaves. And a moss-like tree.
I use a bob sponge filter without the extra lower part.
Also I have one Catappa leaf and banana leaf currently in the tank.
I have also 6 dragon stones, a bit smaller than your hand. One bush wood where the moss resides on and thick driftwood where anubia nana resides on.

I've never had issues with GH as it was around >7°d to >14°d but never more.

GH was always a weird issue at our home, at one time it's perfect and the other day it's not.

I would love to hear of what I can do, remove or add. As stabilzing GH was always weird subject to me. We have PH+KH plus and minus at home, but nothing that helps with GH.

 

Did you put the correct dosage of almond leaf? I know you can get something called equilibrium, which rises gh. However, to lowwr gh usually you need to lower the ph as well, which sucks. I would definitely make sure you got good catappa leaf, because thar always helps with lowering mind.

 

Hey,

There is absolutely no way to lower the GH without affecting the pH and/or KH, too.

Are you sure your measured values are correct, though? Are you using test strips?
I'm asking because they are notoriously inaccurate especially when measuring KH and GH. Having that much of a spread between KH and GH is unusual.

If my assumption turns out correct, you should measure again with drop tests.

Or do you have, by any chance, any stones in the tank that could harden up the water? With a pH that low, I assume you use CO2, some stones can harden up the water quite a bit.

If you don't use CO2, you're measured parameters are completely wrong anyways.
There's no chance you reach a pH of 6.8 at KH 6 without injecting CO2, since that would add up to 26ppm of CO2 in the water. Levels without injecting CO2 are somewhere between 0.5 and 2ppm usually.

Not sure if it's possible where you live, but here in Germany all water suppliers have to publish a detailed water analysis which also includes GH. Maybe you can check if your water supplier has one published somewhere...

 

Did you put the correct dosage of almond leaf? I know you can get something called equilibrium, which rises gh. However, to lowwr gh usually you need to lower the ph as well, which sucks. I would definitely make sure you got good catappa leaf, because thar always helps with lowering mind.

I have one catappa leaf from Tantora brand. As i know you cannot overdo it.

 

I have one catappa leaf from Tantora brand. As i know you cannot overdo it.

Yeah you can't, But what size is your tank?

 

Hey,

There is absolutely no way to lower the GH without affecting the pH and/or KH, too.

Are you sure your measured values are correct, though? Are you using test strips?
I'm asking because they are notoriously inaccurate especially when measuring KH and GH. Having that much of a spread between KH and GH is unusual.

If my assumption turns out correct, you should measure again with drop tests.

Or do you have, by any chance, any stones in the tank that could harden up the water? With a pH that low, I assume you use CO2, some stones can harden up the water quite a bit.

If you don't use CO2, you're measured parameters are completely wrong anyways.
There's no chance you reach a pH of 6.8 at KH 6 without injecting CO2, since that would add up to 26ppm of CO2 in the water. Levels without injecting CO2 are somewhere between 0.5 and 2ppm usually.

Not sure if it's possible where you live, but here in Germany all water suppliers have to publish a detailed water analysis which also includes GH. Maybe you can check if your water supplier has one published somewhere...

Hi, I'm using test strips since it's all what we have. They can be very inaccurate in general as it's hard to tell by the color at times.

As for the stones, no. I only have dragon stone in it which never rised the hardness before. I know some stones rise it but as mentioned it before, it never did. I do use CO2 for the plants, it's possibility i might have added too much but it was never this high in GH for years.

I just did a strip moment ago and noticed the KH became brighter and sits around 3 now. I did last strip a week ago so I remembered where it sat, i did even double strip to make sure i was not mistaken.

Where i live the lowest is 7,34 dH and highest is 7,84 dH, so its hard water but even when I used distilled water it didnt improve.
32 x 32 x 42,5 cm

I've added catappa's leaves before but it never affected GH to be this noticeable.

Did you put the correct dosage of almond leaf? I know you can get something called equilibrium, which rises gh. However, to lowwr gh usually you need to lower the ph as well, which sucks. I would definitely make sure you got good catappa leaf, because thar always helps with lowering mind.

sorry for some reason i cannot replay to your other response.

It's 32 x 32 x 42,5 cm, aka superfish Qubiq 30 pro black tank.

 

With co2 injection OP's numbers make sense... But the problems are just a side effect of injecting co2 (which is acidic) into a tank with dragonstone. Very common issue in planted tanks, wouldnt be surprised if TDS is 500+

Dont think there's an easy solution other than just take out the rocks

 

Hey,

But the problems are just a side effect of injecting co2 (which is acidic) into a tank with dragonstone.

Not sure I understand? Dragon stones don't influence the hardness at all.

 

Hi, I'm using test strips since it's all what we have. They can be very inaccurate in general as it's hard to tell by the color at times.







As for the stones, no. I only have dragon stone in it which never rised the hardness before. I know some stones rise it but as mentioned it before, it never did. I do use CO2 for the plants, it's possibility i might have added too much but it was never this high in GH for years.







I just did a strip moment ago and noticed the KH became brighter and sits around 3 now. I did last strip a week ago so I remembered where it sat, i did even double strip to make sure i was not mistaken.







Where i live the lowest is 7,34 dH and highest is 7,84 dH, so its hard water but even when I used distilled water it didnt improve.



32 x 32 x 42,5 cm







I've added catappa's leaves before but it never affected GH to be this noticeable.







sorry for some reason i cannot replay to your other response.







It's 32 x 32 x 42,5 cm, aka superfish Oh. It's weird your gh isn't lowering than, as Hou do have the correct dosage. Have you tried injections? Qubiq 30 pro black tank.

 

With co2 injection OP's numbers make sense... But the problems are just a side effect of injecting co2 (which is acidic) into a tank with dragonstone. Very common issue in planted tanks, wouldnt be surprised if TDS is 500+

Dont think there's an easy solution other than just take out the rocks

Dragonstone doesn't rise hardness which is my main issue, that my PH is on the lower side is due what I have in my tank and I can easily adjust it. But it doesn't explain why my GH is overwhelmly high.

 

Hey,

what substrate do you use?

Other than that, I assume a measurement error ... GH doesn't just explode like that.
If your tap water is around °7.5 dH and you have inert stones and substrate in the tank, then your tank water is also around 7.5 °dH.

 

Hey,



Not sure I understand? Dragon stones don't influence the hardness at all.

Dragonstone leaches quite a bit... Just because some online store says they dont doesnt mean it's true

 

The around 1 dozen fish tanks I had with dragon stones say the same as the store, though?

Dragon stones are made out of clay, which is completely inert. If they harden your water, your supplier (or whoever created those dragon stones) most likely sells something as dragon stone, that shouldn't be one.

I literally never encountered any dragon stone that altered the water in any way, at least for myself, friends, colleagues, (German) forums.

Maybe it's different in Canada / overseas.

Just for reference, we're talking about these bad boys, right?

Drachenstein - Ohko

 

The around 1 dozen fish tanks I had with dragon stones say the same as the store, though?

Dragon stones are made out of clay, which is completely inert. If they harden your water, your supplier (or whoever created those dragon stones) most likely sells something as dragon stone, that shouldn't be one.

I literally never encountered any dragon stone that altered the water in any way, at least for myself, friends, colleagues, (German) forums.

Maybe it's different in Canada / overseas.

Just for reference, we're talking about these bad boys, right?

Drachenstein - Ohko

Ive never encountered completely inert stones before. All natural rocks leach to some extent and it is depedant on the hardness and acidity of your water. Are you doing co2 injection? I would be surprised if your hardness does not change if you have soft water and pH goes below 7

Dragonstone is well known in planted tanks to leach, same with seiryu stone. It's possible yours might be treated or painted with some resin

In the major petstores here it's common for rocks to be resin covered. But if you break it or scrub it then it will leach again

 

Hey,

what substrate do you use?

Other than that, I assume a measurement error ... GH doesn't just explode like that.
If your tap water is around °7.5 dH and you have inert stones and substrate in the tank, then your tank water is also around 7.5 °dH.

It's a mix between two, fluval plant soil and sand. I forgot the brand name though. But I had it for 3,5 years and it never really affected anything but healthy growth of the plants.

Might be, I genuine don't like using test strips as it can be really hard to tell and it's not accurate.

I did 75% water change and added 10 litre of distilled water and 5 littre with tap water with addition of tetra aquasafe, a bit extreme but I might simply re-cycle it to the point it's correct again. I don't plan to buy a fish before the tank is healthy and stable.

After an hour I did another test strip. Last GH strip is trying to turn blue but its not quite there yet, so I suppose I would need to add distlled water multiple times where the GH finally is balanced out.

I removed both of the leaves. Cleaned all rocks, but removed some little ones. I forgot I had these in it but they are out now. And the sick Anubia Nana has been removed.

Both PH and KH seems to be unaffected as it remains same colors as yesterday.

I do plan to

The around 1 dozen fish tanks I had with dragon stones say the same as the store, though?

Dragon stones are made out of clay, which is completely inert. If they harden your water, your supplier (or whoever created those dragon stones) most likely sells something as dragon stone, that shouldn't be one.

I literally never encountered any dragon stone that altered the water in any way, at least for myself, friends, colleagues, (German) forums.

Maybe it's different in Canada / overseas.

Just for reference, we're talking about these bad boys, right?

Drachenstein - Ohko

Yes, mine look exactly like that. They fall apart slightly in clay-ish way, i think it has to do simply because they are small. Like around 5-7 cm and have quite a lot of holes. When I cleaned them, they were your typical brown-ish clay.

Hey,

what substrate do you use?

Other than that, I assume a measurement error ... GH doesn't just explode like that.
If your tap water is around °7.5 dH and you have inert stones and substrate in the tank, then your tank water is also around 7.5 °dH.

It's a mix between two, fluval plant soil and sand. I forgot the brand name though. But I had it for 3,5 years and it never really affected anything but healthy growth of the plants.

Might be, I genuine don't like using test strips as it can be really hard to tell and it's not accurate.

I did 75% water change and added 10 litre of distilled water and 5 littre with tap water with addition of tetra aquasafe, a bit extreme but I might simply re-cycle it to the point it's correct again. I don't plan to buy a fish before the tank is healthy and stable.

After an hour I did another test strip. Last GH strip is trying to turn blue but its not quite there yet, so I suppose I would need to add distlled water multiple times where the GH finally is balanced out.

I removed both of the leaves. Cleaned all rocks, but removed some little ones. I forgot I had these in it but they are out now. And the sick Anubia Nana has been removed.

Both PH and KH seems to be unaffected as it remains same colors as yesterday.

I do plan to remove some of the sand and place fluval stratum.

 

Are you doing co2 injection? I would be surprised if your hardness does not change if you have soft water and pH goes below 7

Be surprised!

30 ppm, pH around 5.9 in the last tank I had with dragon stones.
All scapes I had with dragon stones so far were anywhere between 20 and 30ppm CO2, pH between 5.7 and 6.2.

No resin covered stones, I would never use those.
Seiryu is known for leaching, yes, I use those in my 35l currently.

I also use river stones in my current 126l, which do not leach (tested them all with ph-/kh-minus and used the inert ones), again CO2 around 30ppm, pH around 6.3ish

Might be regional, no idea. Here in Germany dragon stones are well known for being inert. But yes, after a quick research, it seems like overseas there's quite a bit of dragon stones being sold, that shouldn't be called dragon stones.
The original dragon stones, called Ohko, do not alter the water.

I found this:

 

Ive never encountered completely inert stones before. All natural rocks leach to some extent and it is depedant on the hardness and acidity of your water. Are you doing co2 injection? I would be surprised if your hardness does not change if you have soft water and pH goes below 7

Dragonstone is well known in planted tanks to leach, same with seiryu stone. It's possible yours might be treated or painted with some resin

In the major petstores here it's common for rocks to be resin covered. But if you break it or scrub it then it will leach again

I do add CO2 but it didn't really change anything over the years. So this rise in GH is out of nowhere.

I didn't buy my stones in your typical petstore. Since in my country is known to be Pets Place. Which often has cheap products.

I held some rocks that felt fake-ish, I don't know if thats the right word but it didn't feel right. When my dragonstones arrived, they didn't really feel coated with anything. When it arrived it had it's typical sand clay everywhere in its transport box. I don't know how you treat stones but it def didn't had your typical shine or felt smooth. So I don't think it was coated with resin?

Then again I might be wrong as this is complete new subject to me.

Be surprised!

30 ppm, pH around 5.9 in the last tank I had with dragon stones.
All scapes I had with dragon stones so far were anywhere between 20 and 30ppm CO2, pH between 5.7 and 6.2.

No resin covered stones, I would never use those.
Seiryu is known for leaching, yes, I use those in my 35l currently.

I also use river stones in my current 126l, which do not leach (tested them all with ph-/kh-minus and used the inert ones), again CO2 around 30ppm, pH around 6.3ish

Might be regional, no idea. Here in Germany dragon stones are well known for being inert. But yes, after a quick research, it seems like overseas there's quite a bit of dragon stones being sold, that shouldn't be called dragon stones.
The original dragon stones, called Ohko, do not alter the water.

I found this:

Huh, that's interesting. I didn't knew there is Ohko dragonstone, then again it was my first time trying to aquascape.

When looking at the video, they did had this look when they first arrived. Though they changed some colors now as some of them were deep in substrate and others were a bit higher. I believe one or two of em have more grey-ish brown color now.

I'll attach some photos, sorry for the dirty tank, i'm still in progress of cleaning it up but i removed too much water for now so I'll have to wait for now.

 

Be surprised!

30 ppm, pH around 5.9 in the last tank I had with dragon stones.
All scapes I had with dragon stones so far were anywhere between 20 and 30ppm CO2, pH between 5.7 and 6.2.

No resin covered stones, I would never use those.
Seiryu is known for leaching, yes, I use those in my 35l currently.

I also use river stones in my current 126l, which do not leach (tested them all with ph-/kh-minus and used the inert ones), again CO2 around 30ppm, pH around 6.3ish

Might be regional, no idea. Here in Germany dragon stones are well known for being inert. But yes, after a quick research, it seems like overseas there's quite a bit of dragon stones being sold, that shouldn't be called dragon stones.
The original dragon stones, called Ohko, do not alter the water.

I found this:

But whats the GH and TDS reading? In already hard water the leaching will stop once it hits an equilibrium, but in RO water I would be surprised if no TDS changes

Yes knock offs are the norm in Canada. Very expensive to import rocks all the way from Japan. For OPs rocks, if its dusty from the mail and breaks apart easily I cant imagine that it wouldnt affect water parameters

 

Hey,

GH 6, TDS varied heavily due to the ferts mostly (Estimative Index), but conductance was always around 280-300ys. GH was stable all the way (drip test), from filling the re-mineralized RODI water in until the next water change, depending on the tank I re-mineralized to values between 4 and 6. KH, depending on the tank between 0.5 and 2.

 

I do add CO2 but it didn't really change anything over the years. So this rise in GH is out of nowhere.

I didn't buy my stones in your typical petstore. Since in my country is known to be Pets Place. Which often has cheap products.

I held some rocks that felt fake-ish, I don't know if thats the right word but it didn't feel right. When my dragonstones arrived, they didn't really feel coated with anything. When it arrived it had it's typical sand clay everywhere in its transport box. I don't know how you treat stones but it def didn't had your typical shine or felt smooth. So I don't think it was coated with resin?

Then again I might be wrong as this is complete new subject to me.

Huh, that's interesting. I didn't knew there is Ohko dragonstone, then again it was my first time trying to aquascape.

When looking at the video, they did had this look when they first arrived. Though they changed some colors now as some of them were deep in substrate and others were a bit higher. I believe one or two of em have more grey-ish brown color now.

I'll attach some photos, sorry for the dirty tank, i'm still in progress of cleaning it up but i removed too much water for now so I'll have to wait for now.

Hmm I would remove the rocks and see if it has any effect on the tank parameters. Also would be interesting to see how much it leaches in a bucket of RO water.

Hey,

GH 6, TDS varied heavily due to the ferts mostly (Estimative Index), but conductance was always around 280-300ys. GH was stable all the way (drip test), from filling the re-mineralized RODI water in until the next water change, depending on the tank I re-mineralized to values between 4 and 6. KH, depending on the tank between 0.5 and 2.

That does seem like it's relatively inert at that hardness (ignoring the TDS). Would also be interested to see what effect it has in RO water without mineralization

 

Would also be interested to see what effect it has in RO water without mineralization

If there's any luck involved I might still have one of the old stones in one of my boxes, I'll have a look as soon as I find the time.

 

Hmm I would remove the rocks and see if it has any effect on the tank parameters. Also would be interesting to see how much it leaches in a bucket of RO water.



That does seem like it's relatively inert at that hardness (ignoring the TDS). Would also be interested to see what effect it has in RO water without mineralization

I dont think removing them will be neccasary, i just did another test strip and 3th last row is trying to turn blue. While the last row is getting more blue-er. Per checking nothing changes for worse just better.

It must have been that there was too much hardness in the water for some reason. This might take a few water changes with distilled water as I don't know exactly how high the GH is. But because it took second time to get some affects, i would need to do it at least 2-3 times more.

I forgot to mention (which is on my fault) that this tank was under quarantine when my betta was sick. Don't really have a hospital tank so i was forced to use this tank. I used sea salt as treatment but not too much, like 3 pinches a day. That must have been increased GH dramatically but it I don't know if that is the culprit as i stopped using it after few days by browsing that it's not a good treatment.

 

I dont think removing them will be neccasary, i just did another test strip and 3th last row is trying to turn blue. While the last row is getting more blue-er. Per checking nothing changes for worse just better.

It must have been that there was too much hardness in the water for some reason. This might take a few water changes with distilled water as I don't know exactly how high the GH is. But because it took second time to get some affects, i would need to do it at least 2-3 times more.

I forgot to mention (which is on my fault) that this tank was under quarantine when my betta was sick. Don't really have a hospital tank so i was forced to use this tank. I used sea salt as treatment but not too much, like 3 pinches a day. That must have been increased GH dramatically but it I don't know if that is the culprit as i stopped using it after few days by browsing that it's not a good treatment.

Yes... Sea salt adds GH directly....

 

Yes... Sea salt adds GH directly....

But what confuses me I'm 100% I didn't add one tablespoon of it. My shrimps started to die around 23th of January. But I've added sea salt without knowing better in the end of December for few days.

Does the sea salt stays in the effect even if you did water change?

I'm just asking since it's my sister who bought it and said you can use to help the fish. I recently got into different salts which you supposed to use for freshwater, I got few years later into aquariums than my sister and I used to look up to her what should I do. I don't want the mistake to happen again but if the effect does stay then I'll throw the sea salt away just to be safe.

I'm sorry that it was something completely simple...

 

Couple factors here that are off. The fluval stratum soil should balance the pH between 6.0 and 6.5 depending on what the KH was of the water used and with water changes over time this "buffering between the KH and the stratum will cancel out as the stratum depletes its acidity. And then the KH can normalize. Lifespan of stratum is 2-3 years, acidic soils promote plant growth, the acidity makes nutrients more easily available.

I'd say your pH is high for stratum being used and since the length of time mentioned, likely breaking down at this point and becoming mud under there. Should be replaced roughly every 2-3 years.

Does that have an effect on GH? I'm not sure. Stands to reason over time and the acidity of the soil and the KH of the dragonstone and water buffering against the stratum, theres going to be H ions released..... carbonates getting used up to buffer the acidic soil, and calcium being left the plants would need to use up.

And yeah, not all dragonstone is created equal. There's high grade and low grade.
I'd think a calcium test would tell you how much of that GH is calcium.

I'm gonna think some more on this.

 

Couple factors here that are off. The fluval stratum soil should balance the pH between 6.0 and 6.5 depending on what the KH was of the water used and with water changes over time this "buffering between the KH and the stratum will cancel out as the stratum depletes its acidity. And then the KH can normalize. Lifespan of stratum is 2-3 years, acidic soils promote plant growth, the acidity makes nutrients more easily available.

I'd say your pH is high for stratum being used and since the length of time mentioned, likely breaking down at this point and becoming mud under there. Should be replaced roughly every 2-3 years.

Does that have an effect on GH? I'm not sure. Stands to reason over time and the acidity of the soil and the KH of the dragonstone and water buffering against the stratum, theres going to be H ions released..... carbonates getting used up to buffer the acidic soil, and calcium being left the plants would need to use up.

And yeah, not all dragonstone is created equal. There's high grade and low grade.
I'd think a calcium test would tell you how much of that GH is calcium.

I'm gonna think some more on this.

Oh I did not knew about the fluval stratum breaking down to mud and should be replaced every 2-3 years. Good thing i did buy some new stratum fluval and will replace it in this case.

The GH is most likely due the sea salt with addition that our tap water is quite on hardy side at times. It may simply grew too much GH over time I think?

I plan to get a more accurate tester which I can test more things like Calcium as it really starts to irritate me that I cannot meassure it closer of what should be but I have to guess on the color.

I do appreciate the info, I'm not too wisest when it goes to quality and paramaters. But seeing how you guys check stuff and what should be done. Really gives me more of a better sight what should be done.

 

Hey,

what kind of sea salt? Like for a reef tank or just normal salt you use for cooking?

Asking since the GH tests for our tanks usually just measure the alkaline earth metals ... sodium is not one of them.
I mean that's the principle of ion exchange water softeners, they swap Ca and Mg for sodium -> GH goes down.

If you used salt for a reef tank then yes, those add Ca and Mg. A lot of it even.

 

Hey,

what kind of sea salt? Like for a reef tank or just normal salt you use for cooking?

Asking since the GH tests for our tanks usually just measure the alkaline earth metals ... sodium is not one of them.
I mean that's the principle of ion exchange water softeners, they swap Ca and Mg for sodium -> GH goes down.

If you used salt for a reef tank then yes, those add Ca and Mg. A lot of it even.

It's not for cooking as it was bought from in a aquarium shop where it's a tiny hobbyist.

I dont have anything to meassure Ca and Mg, so i would need to buy testers to see if it indeed affected it.

 

Hey,

if it's "sea salt" from a fish store then it's most likely for reef tanks. Which means a ton of Ca and Mg, the stuff that makes the GH in our tanks.

For reference, reef tanks usually have around 1300mg/l Mg and 420mg/l Ca ... 4.4 mg/l Mg = 1 °dGH and 7.1 mg/l Ca = 1°dGH

So for example 40mg/l Ca and 6mg/l Mg equals GH 7 ... now compare that to the values of reef tank water.

If we take the usual salinity for reef tanks ... it's around 2 tablespoon per liter. Let's say you added 1 tablespoon. That's 650mg Mg and 210mg Ca. Your tank has 30 liter so probably 25 liters of pure water.

That's 26mg/l Mg and 8.4 mg/l Ca.

And that again is 1.18 °dGH from Ca and 5.9 °dGH from Mg ... so you added a total of around 7° dGH in your tank with 1 table spoon.

And tadaa, there's your explanation where the GH came from.

 

Some of the "aquarium" salts can have calcium and magnesium in it. Depends on brand. not sure if this is the case. Some are just sodium chloride, others are mineralized. depends on which you got, and what a person is doing whether they want it mineralized or just salt and mineralizing on their own.
My guess is, the GH is coming from that salt used, I don't use salts at all for my tanks.

My tap water is like a 0-1 dGH, 4 dKH, My tank, due to not changing water for like 5 years and just topping off for evaporation, was like 23dGH, 0KH. pH below 6.0, and nitrates through the roof, and took about a year of slow daily then more extreme water changes towards the end each week, to bring back closer to my tapwater range.

I don't have plants and nowhere for nitrates or minerals to go except build up, and not water changing and just topping off for evaporation, just stacked them up to crazy amounts. while the acids from nitrates and carbons depleted the KH. My fish survived it it was a slow transition, and because I did water changes over a long period of time to correct for it, they survived the transition back to near no GH, some KH, pH finally coming up from lower than 6.0 where my test stopped, and nitrates down to nothing again.Tank was crystal clear the entire time when the water was a disaster, now the water is the best it's ever been and as cloudy as heck.

Not saying this is whats happening to you, your pH is good, but saying mine was extreme neglect and topping off, just not water changing enough each month builds up over time also, takes longer but same result can happen long term.

interesting observation from my situation, the tank water is still killing the grass on the lawn, no idea why, but every time I'm draining, I'm getting a brown patch where the water runs afterwards. I was told aquarium water is good for plants (freshwater) , my other tanks don't do it, THAT tank does it and is still doing it, I'm assuming it's pH related.

Anyways, things can go sideways and this is how we learn, just have to figure it out when it goes sideways to correct the problem. it might be your sea salt addition.
.

 

Hey,

if it's "sea salt" from a fish store then it's most likely for reef tanks. Which means a ton of Ca and Mg, the stuff that makes the GH in our tanks.

For reference, reef tanks usually have around 1300mg/l Mg and 420mg/l Ca ... 4.4 mg/l Mg = 1 °dGH and 7.1 mg/l Ca = 1°dGH

So for example 40mg/l Ca and 6mg/l Mg equals GH 7 ... now compare that to the values of reef tank water.

If we take the usual salinity for reef tanks ... it's around 2 tablespoon per liter. Let's say you added 1 tablespoon. That's 650mg Mg and 210mg Ca. Your tank has 30 liter so probably 25 liters of pure water.

That's 26mg/l Mg and 8.4 mg/l Ca.

And that again is 1.18 °dGH from Ca and 5.9 °dGH from Mg ... so you added a total of around 7° dGH in your tank with 1 table spoon.

And tadaa, there's your explanation where the GH came from.

Oh...oh... thank you for the clear explanation. I did not knew the sea salt was this strong even in tiny amounts. That makes absolute sense now.

I will then keep adding distilled water for few more times until the hardness is on the reasonable level for the freshwater tanks. I'm planning to get the Mg and Ca testers as the one we have at home is a basic and does not specify what is exactly high.

Thank you again for the explanation. I already removed the sea salt from our aquarium equipment as we are not planning to do reef aquarium anytime soon.