GH and KH observations, self adjusting?

JDM

While dealing with my nitrite issue I figured I might as well run more tests to get a better idea of everything that is changing in my tank. I figure the more I know about what it normally does the better able to spot something abnormal in the future. Of course most things are likely only spotted by following certain testing frequencies, like my nitrite spike.

I have noted that my GH and KH drop substantially after adding new water.

dGH of 23 to 17 and dKH 21 to 14 in two weeks. But I didn't know how fast that happened, only where they ended up after the two weeks. Now I think there was one more small change in there, so the results are a little higher than they might be unless this is the bottom of the adjustment range and it happens in a one week window.

10 Days later I did a 75% water change followed by a 30% water change the next day. That's most of the water being replaced, about 83% between the two changes.

New readings = 22 dGH and 18 dKH

2 days later

19 dGH and 17 dKH

My pH hovers around 7.8. A little higher than I like but I am not going to try to change it at this point. Not much sense as that is my tap water.

I've no answers for why this happens but it is interesting that it does. I suspect the plants are the culprits.

Jeff.

Byron

Yes, plants will take up calcium and magnesium so the GH should lower; some plants can use bicarbonates so that works there too.

In my own situation, with near-zero GH and KH in my tap water, I raise the GH at each water change with Equilibrium. When I began this, I raised it initially to 4 dGH. Over a period of several weeks I worked out the amount of Equilibrium I must add at each 50% water change to maintain the GH around 5 or 6 dGH. I haven't tested post-water change, perhaps I will this morning when I do the water changes in a few moments, to see the variation. But from my calculations based upon how much I add and the GH at the end of the week, I am expecting it to be 2 or 3 degrees.

Byron.

Byron

I was able to partly test this, but will have to continue into the week to get the whole picture. What emerged today was no surprise; the GH in each tank is basically what it has always been when tested just prior to the weekly water change [numbers vary tank to tank, but I keep a written record of all tests back a couple years]. And after a 50% water change in each tank this level was cut in half, which is to be expected with a 50% change using near-zero GH tap water.

Equilibrium was added as usual, and today I was careful to use level tablespoons consistently and I wrote the numbers down so I could more accurately judge the results. It takes a while for the E to completely dissolve, so if I can remember, I will test the GH tomorrow morning and post numbers. A day beyond that might be helpful too, just in case it takes longer for E to dissolve, but I wouldn't think that to be the case.

I did discover that my test kit was not working; I assume it has expired, since I was using it over a year ago (autumn 2011) when I began the Equilibrium, and I had it for a year or more prior to that. Today it was not producing much of any colour, and I remembered I had purchased a new kit a couple months back, so I used that.

Byron.

JDM

I doubt that my GH test kit will last that long at 17 to 23 drops per test.

So, are you going to see if the GH drops after full dissolution of the E and prior to the next water change?

What you are doing, albeit intentionally, is similar to what I am doing by default as I add water at 23dGH to water at 17dGH. To me, smaller more frequent changes would be more beneficial to keep the hardness more stable at a consistently lower level as the plants (assuming still that it is the plants here) are not required to draw quite so much out of the water to bring it down. I am thinking that I might see a lower yet GH if I do that.

Having said that, I wonder if doing so will slow the plant growth... I doubt it as my water is plenty hard.

Jeff.

Byron

Yes, the test results will determine if this occurs and to what extent. I doubt it is much, given the small amount of Equilibrium I add. It will be interesting to see what the GH is tomorrow, at its highest which obviously will have to be at or above the level it normally is prior to the water change.

In my situation, with such a low GH anyway, a difference of 2 or 3 dGH is not going to be an issue for fish, and I have never worried about this. But i agree that it is something you should consider, depending upon the fish species.

The amount of calcium and magnesium taken out by the plants would depend upon the plant species (rate of growth, and whether hardwater or softwater plants to begin with), numbers, and of course having all other nutrients and light sufficient. I don't know to what extent plants can store up calcium, if at all. And both calcium and magnesium if overdosed can cause other nutrient deficiencies, but I've no idea what the specific levels need to be for this to occur.

Byron.

JDM

I selected fish that are good up to 20dGH and 30dGH... so the 20 fish would be my largest concern. I think that keeping the levels around 17 should suffice, but if I can get a bit lower then that will be my aim. Hopefully there will be no more large water changes for a while, or at least I can get a jug of RO water to cut if I know ahead next time.

Jeff.

Byron

Now I have the second set of test results. In all tanks, the GH is now exactly 2 dGH higher (with the addition of the Equilibrium) than it was after the water change.

This is not as high as it was prior to the water change, partially explained by my using equal-measure tablespoons this time which has not added as much as I might have done last week when I was much less precise. Also, I did deliberately add less in two tanks.

One needs fairly controlled tests in order to have them practical, so this is fine. It just means I will have to carry this through to next Wednesday's water change in order to have the full picture.

Byron.

TitanTDH

Well that explains why my tank is slowly decreasing gh and kh. Awesome. Tap supply is gh7-8 and kh 1-2. Tank before WC gh 5-6 kh 1. Does prime conditioner affect equilibrium? Asking for my 36g build. So I can get the numbers up a little more

Byron

Prime should not affect Equilibrium, since the latter is primarily only the hard minerals (calcium, magnesium, potassium) which are not heavy metals (copper, zinc, iron, etc) and Prime targets heavy metals. Although I don't use Prime, I use another less bothersome conditioner which also detoxifies heavy metals (most, but not all, do) and together there is no issue.

You are the enviable position of having near-perfect tap water, when it comes to GH for plants. Equilibrium is not cheap.

Byron.

TitanTDH

Yeah mate, pretty happy with the water. Matches the plants and fish I intend to use. Just looking at upping the gh and kh by 2-3 points to allow for plant usage. But I'll discuss that when the background is finished