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PostPosted: Jul 28th, '13, 16:53 
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Hi all
I have read several posts on carbonate and general hardness, and we seem to have the slightly unusual situation of low pH and low carbonate hardness but very high general hardness............but I am not sure if it is actually a problem or not!!

I would appreciate advice/clarification if possible!!

This is our AP system's second winter, so second trout season (though have had our swimming pool set up for 5 years now). We haven't had problems with the fish previously, but over this season have lost about 10 trout. They are all active and feeding well, but every week or two one would die completely unexpectedly.

Water tests seemed fine, though the pH is lower than usual. We added salt, but wondered if it was something dropping in the water that the fish were eating (hence just the odd death here and there when all seemed healthy) such as malabar spinach seeds or tiny little gumnuts......still not sure, but it has resulted in me testing the water more just in case, and getting a GH test kit (not something we had done before).

Water test results are:
Fish tank: Top up water (bore water - not on scheme water):
pH 6 (the kit only reads from 6) 6.4
Ammonia 0.1 0.1
Nitrite 0
KH 70ppm 70
GH 500 (28 drops to turn the sample green!!) 179 (only 10 drops)
Salinity 3-4ppt
Temp 15C

We have shells and limestone (the shells didn't seem to make any difference to the KH) in floating baskets in the fish tank. Apart from testing GH for the first time today, all the other water tests have been pretty stable over the last month or so.
So....apologies for the essay :oops: but I know more detail helps when answering!! Is there enough buffering capacity.....is it a problem having such high general hardness.........should the pH be higher (it has usually been higher-more like 6.7-7, hence adding limestone).....

We would really appreciate some guidance from you -we certainly don't want to keep losing a fish here and there!
Deb and Mack

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PostPosted: Jun 7th, '14, 07:56 
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I see this post is from a while ago, and I'm sad no one commented on it because me new system is doing the same thing but a bit more extreme. (2 drops for the KH to change, and I did over 40 drops on the GH with no change!) my tap water is close to 7.8 pH while my system is hovering between 6-6.4...

Did you ever find any answers to yours??


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PostPosted: Jun 8th, '14, 09:46 
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I believe I've seen dandm post recently. You could try sending him a PM, he might be able to give you some first hand advice. Be nice if there is a known solution you could post back as well.

My feeling is that his pH got too low and this had something to do with the fish dying. While I'm not sure about the General vs Carbonate Hardness and the buffering, I have noticed that it can take a while for the CaCO3 (shells...) to dissolve and it seems that the pH is driven down faster than this can happen (at least this is what I think is happening). The more you feed the harder it is to keep up with the pH drop. It would probably not be as much of an issue with more buffering.

There are other ways to raise the pH which could help get a handle on this while using shells or another form of CaCO3 to build up buffering capacity. I believe some people alternate between these two chemicals to get the job done without causing deficiency in one or the other (they compete for plant uptake along with other cations, if I remember right);

Potassium Hydroxide (KOH) - Used to raise pH and add potassium. 1 T / 1000L every few weeks.

Calcium Hydroxide (Ca(OH)2) (Hydrated lime or Brickie's lime or slaked lime) - Used sparingly and with caution (caustic) to raise pH and add Calcium. Probably adding about 1 tablespoon per 1000L until you figure out what works for your system is a good start.

Remember not to change the pH more than .4 points at any one time for either of these. Might take some water out and adjust then add back in after letting the pH stabilize, to be certain you don't overshoot.

Once I had raised the pH some I would put my CaCO3 in a bag under flowing water somewhere in the system and leave it there until I got the system water where I wanted the pH to be.

That's just my 2cents worth, I may not be right. The people that have had to use KOH and Ca(OH)2 to adjust pH, may have more info for you, on when and how much of each they use.

Cheers


Last edited by scotty435 on Jun 8th, '14, 10:16, edited 1 time in total.

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PostPosted: Jun 8th, '14, 10:15 
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whit_ney and scotty435
We did eventually get some assistance, via another thread where someone was having trouble with pH:

viewtopic.php?f=45&t=20637

This helped to clarify our circumstances a bit more, and realise that by continually adding limestone and shells we weren't actually helping. What we needed was to add Potassium Bicarbonate in the form of 'eco-fungicide' which is readily available though a little costly to help with the buffering capacity.

Apparently many alternate between Calcium Carbonate and Potassium Bicarbonate (much safer to use and keep the KOH that is often recommended too). It took us a while to give it a go, as it didn't seem right to add eco-fungicide, but it has helped. We think now we will do a bit more alternating to try to maintain the balance.

Hope that helps!!
Deb (the d in dandm!!)

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PostPosted: Jun 8th, '14, 10:24 
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Just as an addendum to what Deb just wrote - here's an explanation about the choice of which base you can use to adjust your pH up. It's basically a paraphrase of what Rupe posted long ago -

Note - for raising pH - There are several different ways to do this - from most basic to least basic --> Hydroxides, Bicarbonates, Carbonates. Do not change the pH by more than .4 points during a single application (per Rupe).

Hadn't thought about the buffering capacity of Potassium Bicarbonate mentioned in the other thread. Even though it's not as strong a base as KOH it will help with the buffering and KOH won't.

Thanks for the insight Deb


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PostPosted: Jun 8th, '14, 10:33 
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Just passing on…but thanks for the reminder to do only a small change at a time, had forgotten to pass that on too!


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PostPosted: Oct 9th, '21, 18:19 
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thank you very much for the advice! I was just looking for a discussion on this topic - the same problem began with an increase in water hardness. I'll try to change the base, I hope everything will work out


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PostPosted: Oct 26th, '21, 03:20 
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Hi all,

My first post in this forum. (My second will be in the system description page).

While I felt fairly knowledgable before designing and building, I always knew it was a theoretic knowledge and doing it would teach me a lot more.

Intro aside, I am having this very problem. Have used both calcium carbonate (for one month now) and potassium hydroxide (for maybe one week now) alternating to help but they only raise the pH for a bit and two days later I am adding one of them again; which did not feel right to me.

My KH is low (30-50ppm) while my GH is high (320-380ppm). pH is always bouncing between 6.8 and 6.1

I do have some Potassium Bicarbonate in the mail to me already, so I'm hoping that this helps add buffer that I was missing.

I'll report back in due course.

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