The Incredible Shrinking GH/KH - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 02-12-2014, 11:49 PM Thread Starter
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The Incredible Shrinking GH/KH

I wanted to find out if the rocks I bought would affect water hardness. So I set up a little experiment. I filled two buckets with tap water. I put the rocks into Bucket A and left only the plain water in Bucket B. No filtration or water treatment of any kind. I kept the buckets covered to minimize evaporation. Then I tested GH and KH daily with the API test kit....

On Day 1 both buckets showed GH=9 and KH=5.

Over the course of a week, the GH and KH slowly decreased in both buckets....

On Day 8 both buckets showed GH=6 and KH=2.

Since both buckets match, the rocks don't seem to be causing any problems. But now my question is why is the water hardness decreasing? Shouldn't it stay the same? If water hardness naturally decreases all by itself, then how does anyone ever have hard water in their tank?

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post #2 of 9 (permalink) Old 02-13-2014, 01:29 AM
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That's quite bizarre. You are correct, it is not supposed to do that. The buckets are both plastic, I assume? Only thing I can think of is something is causing the calcium and/or magnesium to precipitate out of solution.
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post #3 of 9 (permalink) Old 02-13-2014, 02:46 AM
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Could be phosphates on or in the rock. Not a geologist. Just a guesser.

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post #4 of 9 (permalink) Old 02-13-2014, 10:53 AM
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Just speculating too.. did you get your water sample for the test from the top, mid level, or bottom of the bucket?

A funny thing I noticed the other day as I was drip acclimating my new critters and playing around with my TDS meter was that the TDS was vastly different depending on the level of the meter in relation to the bag the water was dripping into. Of course, this only showed up because apparently the TDS in the bag was vastly different to begin with. But, what I'm trying to get at was that as the water dripped in, it didn't mix with the stuff in the bag. I had to stir it in myself to get the change that I expected. Could it be that whatever is contributing to the hardness originally is settling?
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post #5 of 9 (permalink) Old 02-13-2014, 02:45 PM
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Another thought. How old are the test kits? Sometimes they get hinky as they age.
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post #6 of 9 (permalink) Old 02-13-2014, 09:02 PM Thread Starter
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Quote:
Originally Posted by chibikaie View Post
That's quite bizarre. You are correct, it is not supposed to do that. The buckets are both plastic, I assume? Only thing I can think of is something is causing the calcium and/or magnesium to precipitate out of solution.
Yes, both buckets are plastic.

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Originally Posted by Jeffww View Post
Could be phosphates on or in the rock. Not a geologist. Just a guesser.
I have no idea about phosphates.....

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Originally Posted by ipkiss View Post
Just speculating too.. did you get your water sample for the test from the top, mid level, or bottom of the bucket?
I took the water samples from the middle of the bucket using a turkey-baster thingy (which has never touched anything but water).

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Originally Posted by chibikaie View Post
Another thought. How old are the test kits? Sometimes they get hinky as they age.
Brand new. I just bought them. In 7 years of fishkeeping, I never tested water hardness before.

55g: Finnex Planted+ and MonsterRay, Pressurized CO2 w/ Atomic inline diffuser, Eheim 2217, Eco-Complete, EI ferts. Lemon, Glowlight, and Black Neon Tetras; Harlequin Rasboras; Otos. Staurogyne repens, Hygrophila corymbosa, Ludwigia repens, Ludwigia glandulosa, Red Melon Sword, Wisteria, Water Sprite.

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post #7 of 9 (permalink) Old 02-13-2014, 09:55 PM
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That really doesn't make any sense whatsoever. At this point, though, I would suspect the test kits even though they are new. They may have sat around in a warehouse and be older than you think, or simply have come from a bad batch. API is not the most reliable manufacturer, despite their popularity. How about trying out the KH kit? Measure your tap water, then add some baking soda and do it again. If you have Epsom salts, do it with the GH kit, too. At least it'll give you an idea if the kits are trustworthy.
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post #8 of 9 (permalink) Old 02-14-2014, 08:53 PM
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Things in rocks that typically leach out are Ca+, Mg+, CO3, PO4, SO4, K+, Fe+++ and a few others.

Now if your gh and kH are shrinking I would test the pH of the water. If the pH is too high some of these things will precip out of the solution. Also phosphate can bind to certain things and make them precip out.

Honestly, though, I don't understand why such a large amount of TDS simply went away. Heh. Weird.

EDIT: Oh yea if you have a TDS meter. Use it and start the experiment again in a new bucket. Monitor the TDS everyday and see what happens.
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post #9 of 9 (permalink) Old 02-15-2014, 08:22 PM Thread Starter
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Originally Posted by Positron View Post
Things in rocks that typically leach out are Ca+, Mg+, CO3, PO4, SO4, K+, Fe+++ and a few others.

Now if your gh and kH are shrinking I would test the pH of the water. If the pH is too high some of these things will precip out of the solution. Also phosphate can bind to certain things and make them precip out.

Honestly, though, I don't understand why such a large amount of TDS simply went away. Heh. Weird.

EDIT: Oh yea if you have a TDS meter. Use it and start the experiment again in a new bucket. Monitor the TDS everyday and see what happens.
Um, what is TDS?

55g: Finnex Planted+ and MonsterRay, Pressurized CO2 w/ Atomic inline diffuser, Eheim 2217, Eco-Complete, EI ferts. Lemon, Glowlight, and Black Neon Tetras; Harlequin Rasboras; Otos. Staurogyne repens, Hygrophila corymbosa, Ludwigia repens, Ludwigia glandulosa, Red Melon Sword, Wisteria, Water Sprite.

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