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post #1 of 10 (permalink) Old 09-24-2015, 05:19 AM Thread Starter
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So I've been trying to get a tank to grow plants and its been nothing but mysterious problems till now. I didn't know the tank wasnt being filled with city tap (what i use) till now. Turns out the building is on a well. I checked Gh and got something in the low 40s. No joke. So just how toxic is this level for most plants?
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post #2 of 10 (permalink) Old 09-24-2015, 10:18 AM
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So I've been trying to get a tank to grow plants and its been nothing but mysterious problems till now. I didn't know the tank wasnt being filled with city tap (what i use) till now. Turns out the building is on a well. I checked Gh and got something in the low 40s. No joke. So just how toxic is this level for most plants?
40 what 40 drops, 40 ppm?


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post #3 of 10 (permalink) Old 09-24-2015, 11:27 AM
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40ppm of GH (2.2dGH) is soft water, 40dGH (714ppmGH) is very hard water. Very different results based on your units. What are your units of measurement? The conversion factor per Wikipedia is 1 dGH corresponds to 17.848 ppm.
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post #4 of 10 (permalink) Old 09-24-2015, 01:16 PM
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I am going to assume it is 40 German degrees of Hardness, based on 2 factors:
OP asks 'how toxic is it?' and that implies a high level.
Wells are often in limestone or related rock, and this adds GH, KH, and raises the pH.

However, the other answers are exactly right: Always include the units!

That high level might be a problem if the Ca:Mg ratio is very skewed, but it would have to be way off. Plants use Ca and Mg in a ratio of 4 parts Ca: 1 part Mg, but the water does not have to be that ratio. Just so long as it supplies both in a reasonable ratio. When either are extremely out of line the excess can block the uptake of the other.

The high level could be a problem for some of the highly specialized plants that demand low mineral levels (especially low Ca). These plants are not commonly seen in the aquarium plant stores, though.

I do not know if this happens with Ca or Mg, but...
When some minerals are present in excess they block the plant from picking up certain other minerals. Gotta look into this more, and see if it can happen when Ca or Mg are high.
later...
Yes, it can.
Excess Ca can block the uptake of Mg, and B.
Excess Mg can block the uptake of Ca.

If other minerals are in excess they can block the uptake of...
Excess... Blocks
..N..........K
..K..........N, Ca, Mg
..Na........K, Ca, Mg
..Ca........Ca, B
..Mg........Ca
..Fe........Mn
..Mn.......Fe

When the GH is high because of limestone in the aquifer, the KH is almost always really high, too. What is the KH? This would also imply that the pH is very high. (is the pH over 8.0?)This would be more of a problem. At high pH many of the minerals plants need are chemically bound up in a way that the plants cannot get them. Nutrient deficiencies would show up, even if the element is present in the tank.

Last edited by Diana; 09-24-2015 at 01:31 PM. Reason: *
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post #5 of 10 (permalink) Old 09-24-2015, 03:15 PM
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If it's limestone, it's CaCO3, Calcium Carbonate.

CaCO3 has a molar mass of 100.0869 g/mol, and with a nice even weight of 100, it makes it easier to do the maths.

The Calcium in CaCO3 is 40% by weight, with Carbonate taking up the remaining 60% of weight. In other words, if some amount of CaCO3 raises TDS by 100ppm, the net result is 40ppm (2.24dGH) Calcium and 60ppm (3.36dKH) Carbonate.
I've created a spreadsheet here, based on the maths from here. Ignore the Na results far right for now, I haven't confirmed the maths.

Note: Both CaCO3 and KHCO3 (Potassium Bicarbonate) have virtually the same molar mass, but KHCO3 only contributes half KH for the same weight as CaCO3.

Quote:
Now the carbonate ion can take 2 H+ ions (to make carbonic acid H2CO3), whereas bicarbonate takes 1 H+ ion (to make carbonic acid H2CO3). Therefore bicarbonate contributes half as much to kH than carbonate, which must be allowed for in any calculations.
edit: Even though the ppm of Calcium and CO3 in the solution is different, their CaCO3 equivalent hardness is equal (in this case 5.6 German degrees).

Last edited by Audionut; 09-26-2015 at 05:35 AM. Reason: Correction regarding hardness
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post #6 of 10 (permalink) Old 09-24-2015, 03:19 PM Thread Starter
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Sorry, degrees/drops. Not ppm.
So basically clear cement.

Bump:
Quote:
Originally Posted by Diana View Post
I am going to assume it is 40 German degrees of Hardness, based on 2 factors:
OP asks 'how toxic is it?' and that implies a high level.
Wells are often in limestone or related rock, and this adds GH, KH, and raises the pH.

However, the other answers are exactly right: Always include the units!

That high level might be a problem if the Ca:Mg ratio is very skewed, but it would have to be way off. Plants use Ca and Mg in a ratio of 4 parts Ca: 1 part Mg, but the water does not have to be that ratio. Just so long as it supplies both in a reasonable ratio. When either are extremely out of line the excess can block the uptake of the other.

The high level could be a problem for some of the highly specialized plants that demand low mineral levels (especially low Ca). These plants are not commonly seen in the aquarium plant stores, though.

I do not know if this happens with Ca or Mg, but...
When some minerals are present in excess they block the plant from picking up certain other minerals. Gotta look into this more, and see if it can happen when Ca or Mg are high.
later...
Yes, it can.
Excess Ca can block the uptake of Mg, and B.
Excess Mg can block the uptake of Ca.

If other minerals are in excess they can block the uptake of...
Excess... Blocks
..N..........K
..K..........N, Ca, Mg
..Na........K, Ca, Mg
..Ca........Ca, B
..Mg........Ca
..Fe........Mn
..Mn.......Fe

When the GH is high because of limestone in the aquifer, the KH is almost always really high, too. What is the KH? This would also imply that the pH is very high. (is the pH over 8.0?)This would be more of a problem. At high pH many of the minerals plants need are chemically bound up in a way that the plants cannot get them. Nutrient deficiencies would show up, even if the element is present in the tank.
Wow, thank you, that was highly informative. I started to check the KH and after 20 just tossed up my hands and said "what the heck is this stuff?!" (our city tap is somewhere around 8kh and 12gh I believe) and gave up, because I wasn't looking to figure out the source water stats at the time, I was just ensuring my own dosing of the tank was correct by making sure I hadn't given too much Equilibrium, which I have to use a tiny bit of in my own (city tap) tank. When it got that high I realised there was WAY more going on here than my adding 1/8th tsp Equilibrium to our city tap and it took me some time to find out the water was well water. This also explains the high nitrate contents in the tank, despite high filtration and sparse feeding, as the well water tests out at ~9ppm nitrate. When you top off regularly and have no plants, this number climbs. As a result, I spent a LOT of time last year doing 50% water changes on this tank, in an attempt to keep the Nitrate from hitting toxic levels. I always assumed the fish were over fed, but now I see the truth.

I'll check the pH and the Kh and get those numbers posted as soon as I can. This helps explain a LOT of strange things that happened in this tank over the last year. Always, always, always check your water source before assuming you know what it has in it I suppose.
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post #7 of 10 (permalink) Old 09-28-2015, 04:34 PM Thread Starter
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Sorry for the long delay, here's hoping some of you are subscribed to this thread still...

For reasons that will waste time to explain, I only have a chance to check this tank's parameters about once a week, so it took a while to get these results.

The pH straight from the tap is about 7.5

I'm not sure if the tap off-gasses CO2 though, as I didn't think to grab a sample from the tank as well. So the pH may actually be a smidge lower, though I wouldn't think there would be a ton of dissolved gasses in well water.

As for the GH and KH they are:
GH is about 8 degrees (hard to tell if it was 7, 8, or 9)
KH is 15 to 16 degrees

wait... WHAT?
When I tested the tank it was in the FOURTIES for GH. Did I read it wrong? I'm heading back to grab another few samples. One from the tank to see if the GH is still 40 something, and one from the cold tap, after running it 5 minutes. As the sample I took was from the hot tap. This is getting stranger every minute.

There must be SOMETHING wrong in the tank, as my guppy grass shoots that I planted are beginning to die, the jungle val is too, and they have adequate light and ferts.
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post #8 of 10 (permalink) Old 09-28-2015, 08:30 PM Thread Starter
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I have a guess as to the problem.

Looks like the laterite clay in the bottom of the tank is leaching more than expected. I didn't use a sand cap on it like I usually do, and as a result it's leaching into the water column and giving me very high gh readings and some higher kh readings as well. *sigh* looks like this tank will need to be re-scaped. Given the fact this has been done a few times already and it's yet to be successful for various reasons, please learn from my mistake, and always, always plan your tank well before setting it up. It's a good thing I started this hobby with a 10 gallon, if I had started it with this 40 gallon tank I never would have enjoyed the hobby one bit, as I have spent so much wasted time on fixing my mistakes with this larger tank, and the larger it is, the more work it is to empty and re-scape.

To confirm this I've set a glass of tap water with the clay in it to sit for a few hours, after which I'll test for a gh increase. Meanwhile I should be able to get the cold water and tank water samples I need to confirm that the high gh is seen only in the tank, not in the tap water.

Last edited by Blacktetra; 09-28-2015 at 08:42 PM. Reason: spelling
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post #9 of 10 (permalink) Old 09-28-2015, 08:33 PM
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Quote:
Originally Posted by Blacktetra View Post
I'm not sure if the tap off-gasses CO2 though, as I didn't think to grab a sample from the tank as well. So the pH may actually be a smidge lower, though I wouldn't think there would be a ton of dissolved gasses in well water.
Leave a cup of water out over night and retest the pH.

Quote:
Originally Posted by Blacktetra View Post
As for the GH and KH they are:
GH is about 8 degrees (hard to tell if it was 7, 8, or 9)
KH is 15 to 16 degrees

wait... WHAT?
When I tested the tank it was in the FOURTIES for GH. Did I read it wrong? I'm heading back to grab another few samples. One from the tank to see if the GH is still 40 something, and one from the cold tap, after running it 5 minutes. As the sample I took was from the hot tap. This is getting stranger every minute.
If you tank is 40dkH and your tap is 8dkH then something in the tank is raising the kH. What kind of rocks are in the tank?


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post #10 of 10 (permalink) Old 09-28-2015, 09:44 PM Thread Starter
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If you tank is 40dkH and your tap is 8dkH then something in the tank is raising the kH. What kind of rocks are in the tank?
See above post. Likely the clay, testing right now to confirm.

Tank Gh is 45 dgh
Tank KH is about 14 dkh

tap water being put into the tank is:
20 dgh
14-15 dkh

This shows no rise in KH but huge rise in GH.
Water with clay in it has been sitting roughly an hour or two.
It rose about one degree GH in that time.

My high GH I conclude to be a result of the clay leaching far more rapidly than my other tank that uses this clay, partly due to lack of a sand cap slowing the leaching process, and partly due to the fact this tank isn't established and heavily planted, and as a result, eating up much of what is being leached.

Time to clean it all out and start over.

Last edited by Darkblade48; 09-29-2015 at 09:10 AM. Reason: Please use the edit function for back to back posts
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