Sorg67
I tested GH recently. The instructions say to keep adding one drop at a time until the color turns from orange to green. In my case, it was a very faint green after the first drop. I keep adding drops thinking that it should start out orange and change to green, but it never showed any hint of orange.

That would have the general hardness between zero and 17.9. My KH reading was about 125.3.

The GH reading seemed really low to me so I checked the tap water and got the same reading.

We have a water softner so perhaps that is the impact of that. I will go test the water before the water softener to see if it is different.

In the meantime, I am wondering if this is something I should worry about.

PascalKrypt
Sounds about right (both your estimation of the value and that the water softener may cause it). Your KH being at 5 is also not super high, the GH might be something around that value originally and have dropped due to the softener. This is pretty the on par with my brother's tap water (he lives in a different city, they have a GH of 7 before the softener and somewhere around 2 after).

If you want to keep shrimp or ornamental snails, this could be a problem. It would help keep pest snail populations under control (they have trouble in tanks with GH <4).
It can be a problem for fish that prefer harder water, like most popular livebearers (the endlers and guppies you want to breed).
You can look into getting some mineral rocks, like chalk-based ones, that can stably raise the GH of your tank a few degrees.

Sorg67
PascalKrypt thanks for the useful and informative feedback.

My GH and KH test works by adding drops one at a time. There is a conversion table to convert the number of drops to a ppm value. My KH was seven drops which converted to 125.3 ppm (an oddly precise number). That seems on a different scale than you are indicating with your value of 5. What are these different scales and how do I convert?

[EDIT] I found a conversion online of ppm to dKH. Multiply ppm by 0.056 to get dKH. That would put me at 7 which is also the number of drops that resulted in that value. Is that a coincidence or by design. You indicated a KH of 5. Is that a different scale?

[EDIT 2] I found a conversion calculator that has three values. mek/liter, dKH and ppm. My KH reading converts to 2.5, 7 and 125.3 respectively. When you say adjusting by a couple degrees, is that on the dKH scale?

[EDIT 3] dKH stands for degrees of Karbonate Hardness. So I am guessing that is the scale you are talking about. But I get 7 rather than 5.

[EDIT 4] Looks like both GH and KH are on the same scale. One degree is 17.9. The reciprocal of that is 0.056. This appears to be the reason for the oddly precise conversion. Each drop appears to be calibrated to one degree.

The GH was one drop. I have still not tested the water before the water softener. I will test that today.

I have assassin snails in the tank. Will this be a problem for them. They seem fine so far. I also have some pest snails, but the assassins seem to have reduced that population significantly.

I have read that it is better to stabilize PH, GH and KH rather than adjust. My PH has been stable at about 7.6. Tank water and source water is the same.

The crushed coral has been recommended several times in threads I have read. Do I understand correctly that it is a gentle water adjustment mechanism that will not cause dramatic swings?

PascalKrypt
PascalKrypt thanks for the useful and informative feedback.

My GH and KH test works by adding drops one at a time. There is a conversion table to convert the number of drops to a ppm value. My KH was seven drops which converted to 125.3 ppm (an oddly precise number). That seems on a different scale than you are indicating with your value of 5. What are these different scales and how do I convert?

[EDIT] I found a conversion online of ppm to dKH. Multiply ppm by 0.056 to get dKH. That would put me at 7 which is also the number of drops that resulted in that value. Is that a coincidence or by design. You indicated a KH of 5. Is that a different scale?

[EDIT 2] I found a conversion calculator that has three values. mek/liter, dKH and ppm. My KH reading converts to 2.5, 7 and 125.3 respectively. When you say adjusting by a couple degrees, is that on the dKH scale?

[EDIT 3] dKH stands for degrees of Karbonate Hardness. So I am guessing that is the scale you are talking about. But I get 7 rather than 5.

[EDIT 4] Looks like both GH and KH are on the same scale. One degree is 17.9. The reciprocal of that is 0.056. This appears to be the reason for the oddly precise conversion. Each drop appears to be calibrated to one degree.

The GH was one drop. I have still not tested the water before the water softener. I will test that today.

I have assassin snails in the tank. Will this be a problem for them. They seem fine so far. I also have some pest snails, but the assassins seem to have reduced that population significantly.

I have read that it is better to stabilize PH, GH and KH rather than adjust. My PH has been stable at about 7.6. Tank water and source water is the same.

The crushed coral has been recommended several times in threads I have read. Do I understand correctly that it is a gentle water adjustment mechanism that will not cause dramatic swings?
Oh sorry, KH and GH are often expressed as easy shorthand as dGH and dKH (the 'd' standing degree). Every 17.8ppm counts as 1 degree. Actually your tests are just measuring dGH/dKH and converting it back to ppm for you, that's why you are getting such an oddly specific number (not because it is actually that specifically accurate). The drop tests are calibrated so that 1 drop equals 1 degree.
Which means that, for instance, if you do the KH test and after two drops your see the colour change, then your KH is somewhere between 1 dKH and 2 dKH, so between 17.8 ~ 35.6 ppm.
(You can tell a bit more accurately depending on how the colour transitions. If it is a suddenly, sharp transition then the ppm value is in the middle of that range, if the colour changes clearly but the change itself is a little slower and takes a few second, then it is closer to the top of that range, if it already started to change colour slightly at the previous drop then the value is closer to the lower end of that range).

Well I typed all of that up and then read your edits. I'll leave that text there in case it still helps clear up some doubts/confirms your story.
(Yes sorry about the '5', that was my typo, whoops. It clearly is 7)

Assassin snails are extremely hardy, mine have survived a month in a crashed tank with GH 0 (the pest snails had to be constantly imported from other tanks because they could not reproduce in that GH). They won't do very well though, a GH of 3+ seems to be best for them.

And yes, 'fighting' your natural water parameters is a very bad choice and something that should only be done if you want to keep specialised fish that are extremely sensitive to living outside their specific natural environment. Pretty much all fish that are common in the trade have adapted to a very wide range of water values and will do just fine. What fish cannot deal with is sudden swings in parameters. The bodily functions of fish are strongly dependent on a process called osmoregulation (you may know this, but I'll just explain from scratch in case not). Osmosis is a process whereby water has a natural tendency to dilute, meaning that water molecules (H2O) are attracted to the highest concentration of salts in water and move naturally to dilute this until all concentrations within range of where the molecules can travel is equal. The cells of living organisms are semi-permeable, meaning they allow water and very small compounds (like some hormones) to pass through, whereas larger compounds such as salts and proteins cannot. This means that water has a tendency to be attracted to cells that contain a higher concentration of salts than the surrounding fluids, and will flow out of cells with a lower concentration.
Thus to prevent imploding or exploding, a fish whose cells are constantly surrounded by water (specifically the gills that water flows through to absorb oxygen) strongly need to regulate this with specific mechanisms. Adjusting these mechanisms to correct the osmotic balance takes time. This is one of the main ways in which a fish needs to 'adapt' to a new environment.
GH and KH (and PH indirectly) are all indicators of this osmotic balance (you can measure more directly with TDS, total dissolved solids, though this is still not the whole story as charges of ions also come into play). If they swing, your fish will struggle to constantly adapt its osmoregulation. This is enormous burden on the fish and thus a large source of stress, that leaves the fish vulnerable to disease.
On the other hand, any specific extreme value may take the fish some effort to adjust to, but once it is set in that environment, it is no further cause of stress because the fish is functioning in it and only has to maintain the internal processes that are already set in place.

The measurements of PH/GH/KH are all just indicators of the results of many interlocked, complex processes that go on in your tank, not all of which are in your total control. Hence why even people with high tech tanks sometimes get their fish wiped out because a carefully measured injection of this or that substance that always yielded a stable result suddenly does something weird. It happens.
Hence, not messing with these processes is almost always better than trying to achieve a perfect set value, as very rarely will you be able to change some of these indicators without impacting the others, which then again impact others, and so on.
(Moreover there are other effects of these indicators than just osmoregulation, but that is the most direct one)

7.5 is a perfectly good PH. I would be hard-pressed to think of any commonly traded fish that would not do well in that. No reason to change that at all.

And yes. Substances like crushed coral and shells and limestone rocks and indian almond leaves and alder cones are all examples of natural items that can be placed in a tank and that will make small, constant and stable adjustments to PH, GH and KH because they are constantly leeching very small amounts of substances in the water that are measured by these indicators, or that trigger a slight tip in the balances of the processes the indicators measure.

Sorg67
PascalKrypt I just re-read you very detailed and helpful explanation. Thank you for putting so much detail. Very helpful.

I also tested the water before the softener and confirmed that the GH value is significantly higher (around 6). KH about the same and PH a bit higher.

I would like to be able to pull water from before the softener. I have another thread open on this issue. Should have put them in one thread.

Anyway, I am considering Seachem Equilibrium. I have been having some issues with plants and this could explain why. I am wondering if this could be a situation in which fighting the water supply could make sense since I am going back to the source levels. Maybe treat moderately just to get GH up just a bit.

Also wondering if in this case many small water changes with small Equilibrium dosages would be prudent to avoid shocks. Maybe I should also test water before changes. Test source water and calculate Equilibrium dosage base on actual values. They may change from time to time.

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