Tap water KH shifts, what to do? - The Planted Tank Forum
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post #1 of 24 (permalink) Old 06-16-2015, 03:22 PM Thread Starter
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Tap water KH shifts, what to do?

So, about a month ago, I lost a cory following a weekly 50% water change, and found that my tap supply GH and KH had dropped. In particular, KH (really alkalinity, this is an API test) went from 4 to 3 dKH and GH went from 7 to 5 dGH at the tap.
https://www.plantedtank.net/forums/sh...577&highlight=

I normally boost GH up to ~10dGH with Equilibrium, and the KH stays at tap levels.

Last night, I did another water change, and this morning found another dead cory.

I tested the tank this morning, and found that it was at 9 dGH and 6 dKH. I did not have time to test the tap, but I assume the tap jumped quite a bit in KH causing this. I have nothing in-tank that raises KH, save one single quarter-sized clamshell that has been there for months as a calcium supplement for the snails.

So, assuming it is the tap, what do you do when your municipal tap supply has variable KH levels?

I could in theory pick some target KH and always boost to that, but what if the supply ends up going way higher? Wait it out and delay your water change? Do a smaller w/c to slowly shift?

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post #2 of 24 (permalink) Old 06-16-2015, 04:38 PM
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Buckets work wonders for adjusting water parameters before anything goes into the tank. Just fill as many buckets as you need for a water change a few days in advance and change what ever needs to be changed. If something is too low boost it up higher. If it's too high then add some RODI or distilled water to bring it down. If you do it a few days in advance, you would also get the benefit of being able to check it again to make sure the parameters are stable before anything goes into the tank.

If the tank is small you can easily get by with a couple 5 gallon buckets or jugs for less than $5 each. If you have a large tank you can get a 55 gallon rain barrel for about $50-$75 at any home improvement store.
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post #3 of 24 (permalink) Old 06-16-2015, 05:04 PM Thread Starter
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Ok, so I'm doing a 36 gallon tank plus a 10 gallon tank. The bucket method, while possible for some, is not an option for my setup.

I don't have the storage space for buckets of water, except in the basement. I'm not lugging a net total of 12-18 gallons of water up from the basement every week to do my w/c's. I love my tanks, but that level of effort would basically force me to quit the hobby.

Storage on the same floor as the tanks isn't really an option. My tanks are on the main floor of the house, which has near zero storage space, just a pantry and a single 2' wide coat closet, both of which are already crammed full. Leaving buckets out on the main floor isn't an option, as this would run afoul of my wife's aesthetic demands for the main floor of the house. My tanks are in a room that is visible from the street, and where guests enter the house... I don't have a separate "tank room" where my tanks are hidden away, they're part of our living and entertaining spaces.

My current changes are done tap-to-tank, with a small 2 gallon bucket being used to pre-dissolve my dose of equilibrium. I am really reluctant to change the general method of water changes much, at least in terms of level of physical work and time.

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Last edited by mattinmd; 06-16-2015 at 05:08 PM. Reason: detail added
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post #4 of 24 (permalink) Old 06-16-2015, 07:34 PM
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I am not convinced that a swing of a point of hardness would kill your fish. When I first started doing RO water I screwed up and did a 50% change with water that was about 4 degrees harder and 3 dkh more than the tank and while they showed signs of discomfort all of them lived. What are your other parameters?
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post #5 of 24 (permalink) Old 06-16-2015, 08:13 PM Thread Starter
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So "normal" for my tank, other than the GH/KH shifts noted above:

dGH 10 (not calibrated)
dKH 4 (calibration checked)
Temperature 77F
pH - don't care, see KH.
NH3/NH4 - 0ppm (below limits of API test, calibration loosely checked)
NO2 - 0 ppm (below limits of API test, calibration loosely checked)
NO3 - 20-30ppm (salifert test, calibration checked, although I haven't tested this since I cut back NO3 and culled fry a month ago, may be lower now)
PO4 2ppm (not calibrated)
API CO2 booster dosed at 1.4x label rate daily.
EI low-light fertilization with reduced KNO3/K2PO4 due to high stock (platties keep breeding like mad) and increased K2SO4 to cover the potassium hole..
Water changes - 50% weekly, tap-to-tank, with water somewhere between 76F and 77.5F

Note that the cories here are bronze cories (corydoras aeneus), chosen specifically to handle the slightly warmer temps and moderate hardness demanded by the mollies present in the tank.

Also, in the case of this death, the KH went from 3dKH to 6dKH, which is 3 degrees different and an overall doubling of alkalinity.. that could prove fatal.

The prior death seems a bit sketchy, but I did note the parameter shift as a plausible cause.

Further notes on the cories themselves:
None of the cories are showing any signs of problems prior to death. Their barbels are all nice and long with no signs of errosion, and they happily dig around the substrate, rest on my anubias leaves, and rarely pop up to the surface for a gulp of air before swiftly bolting back to the bottom. All of that is normal corydoras behavior.

The first dead fish looked normal, other than having a few snails on him and being dead he had the general appearance of being in fine health. Fins all present, barbels intact, no swelling, no redness, etc.

The second fish had his tailfin removed, which may or may not have occurred post-mortem. This one was heavily covered in snails. Other than the torn off fin, he otherwise appeared healthy.

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Last edited by mattinmd; 06-16-2015 at 08:32 PM. Reason: added more notes on the deaths.
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post #6 of 24 (permalink) Old 06-17-2015, 12:59 AM
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The morning of the water change run enough water into a garbage can to do the water change.
Run a small filter on it with Safe-T-Sorb, Turface, or other montmorillonite clay in the filter. Or rig up a fountain pump to make the water flow through these. Or put a 2" deep layer on the bottom of the garbage can and turn on a bubbler from under the substrate.

ANYTHING so you are making the water come in contact with the Safe-T-Sorb.

These materials remove KH.

When the level gets to where you want it, siphon or pump out the water (if the Safe-T-Sorb is loose in the can) or remove the filter.

Then check the GH, and adjust as needed. IME these materials do not remove the calcium or magnesium, but since you want to adjust it anyway, do it after the water is no longer in contact with the STS.

Actually, I would maintain a higher KH for the Mollies, and adjust the water up to that.
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post #7 of 24 (permalink) Old 06-17-2015, 01:40 AM Thread Starter
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Ok, so I did some more testing this evening...

My test this morning that came back 6dKH must have been contaminated. This is actually plausible, as I noticed I spilled some baking soda on a counter near where the test caps were...

Regardless:

My tank is just barely over 2 dKH, the second drop of solution turns the water from blue to a green, but not quite all the way to that yellow color it turns when fully reacted. I tested the tan 3 times, and tap 3 times, and all came back like that.

So, it is another KH dip, not a spike... This makes some sense as it has been rather rainy lately, so the amount of ground-water vs fresh runnoff rain is going to be lower.

This is actually better, as I can just start testing my tap KH when a do a water change, and add enough alkaline buffer and/or baking soda to make the tank end up at 4 dKH... (although per Diania, I might opt to keep it a bit higher, around 6 or so, and just add more or less depending on the tap KH, I'll have to think about that one some).

As for trash cans, etc, that might be doable, although I'll have to grab some kind of pump that can drive the water out of the trash can and into my tank... I'd rather not bucket-lift the water into the tank by hand.

I also tested my NO3, which is now just over 10ppm (day after w/c), so it looks like I'm in a 10-20ppm cycle instead of 20-30ppm...

Does it make sense that KH crashing from 4 to just over 2 could be lethal? We're talking something on the order of 1.5-2 dKH drop, and admittedly ending up rather low on the KH scale...

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post #8 of 24 (permalink) Old 06-19-2015, 06:25 AM
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With such a low KH a PH shift is more likely.
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post #9 of 24 (permalink) Old 06-19-2015, 12:08 PM Thread Starter
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Well, yes, that is obvious.. particularly considering our KH tests aren't really KH, but rather total alkalinity tests by acid titration, and reported in German degrees...

That said, I don't think pH shifts, in absence of KH/alkalinity shift, really matters to fish. If it did, then CO2 injection based pH shifts, pretty much the only way to cause pH shifting without KH shifting, would kill fish.

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post #10 of 24 (permalink) Old 06-19-2015, 01:26 PM
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Generally fish handle the pH shift from CO2 just fine. When the pH shift is because of mineral levels (just what we are talking about here) then it is the shift in mineral levels that is the problem, not the change in pH.

I do not think a KH shift from 4 down to 2 would bother most community fish that are OK with soft water, but perhaps the most delicate fish? Wild caught?
Especially if the GH stayed the same.

Is the GH staying the same?

Do you have a TDS meter? I'll bet this is it:
If the rain is enough to dilute the KH, then it is probably also diluting all the other minerals and salts in the water. Fish do not handle the drop in mineral and salt levels very well, if the drop is more than 10% less than what they were used to.

Yes, get a pump to lift the water from garbage can to tank. This can also circulate the water to mix whatever minerals you need to add.
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post #11 of 24 (permalink) Old 06-19-2015, 02:08 PM Thread Starter
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Quote:
Is the GH staying the same?
The GH of the tap is also shifting, and I've been compensating for that with increased equilibrium dosing...

At the last death I undershot my target GH of 10 and ended up at 9, but that's only a 1 dGH miss... However, it might be exacerbating the problems of the 4dKH->2dKH shift.

Quote:
Do you have a TDS meter?
I do have a TDS meter, but have not been using it regularly. I can start tracking that.


There's one other oddity at play:

I normally dissolve my equilibrium (normally 2tsp, lately 2.5) in a 2 gallon bucket of tap water with .5ml of prime added.

For some reason, I have yet to determine why, the equilibrium sometimes dissolves easily, and other times it clumps up and is very difficult to dissolve.

I have proven that the clumping isn't simply GH related.. I've had two weeks where the GH was the same out of the tap, but one week it clumped and the other it dissolved easily..

I'll have to take some more measurements and basically track Tap GH, Tap KH, Tap TDS, Tap phosphate, and equilibrium dissolving behavior over time, and see if I can relate it to something...

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post #12 of 24 (permalink) Old 06-20-2015, 12:43 AM
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I have a hard time dissolving Seachem Equilibrium.
I put the total amount in a jar with a tight lid (small canning jar) and shake like crazy.
Then decant the milky liquid into the water prep container.
Add more water to the jar and repeat until it is all dissolved.

I found Barr's GH booster easier to dissolve, but I understand they are supposed to be the same.
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post #13 of 24 (permalink) Old 06-20-2015, 03:45 AM Thread Starter
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Diana,

My point was not about Equilibrium being hard to dissolve, or needing to find ways.. my point was the fact that how easy it is to dissolve in my tap water varies, by quite a lot.

I always start with a 2 gallon bucket of 77F tap water... Sometimes dissolve the stuff with great ease, I just toss it in and whirl a few times with a spoon and poof, all done. Other times I put it in and end up with literally 1/2" diameter balls of the stuff clumped up all over the bottom of the bucket, as if it was being severely repelled by the water. I have to mash these balls down with the back of a spoon, because they are hard and solid.. Even after all that I end up with a huge amount of sediment in the bottom of the bucket.

I think this indicative of water parameter variation. The question is, what parameter... Does my water sometimes contain some kind of agent that precipitates calcium, causing equilibrium to not dissolve? Phosphate buffers? My original thought was the water was so high in GH that it wouldn't dissolve, but I already disproved that one (although I may want more data to call it solidly disproved..)

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post #14 of 24 (permalink) Old 06-20-2015, 05:37 AM
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It'll be the calcium sulphate causing solubility problems since you can only dissolve 2.4 grams per liter at best. Bar water temperature, this doesn't change.

Time to break out that TDS meter and create a log so that you're not second guessing yourself.
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post #15 of 24 (permalink) Old 06-20-2015, 06:27 AM Thread Starter
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2.4 grams of Ca2SO4 2H2O per liter is enough for over 78 dGH from calcium.... I'm nowhere near that saturation point, not even anywhere close.

That said, it is the least soluble of the products in equilibrium... however, given the low dGH that this problem occurs at, this isn't a simple saturation problem. I'm betting there's some ion involved that reacts with calcium sulfate to make a much less soluble compound, like calcium carbonate (0.13 g/L solubility), or dicalcium phosphate (0.2 g/L)



That said, I agree, a logbook and parameter measurement is in order, as I already suggested I should do in post 11...

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