SAFELY reduce gh/kh in an existing tank - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 09-30-2014, 02:06 PM Thread Starter
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SAFELY reduce gh/kh in an existing tank

I need to find a way to safely reduce the water hardness and ph in a tank with existing flora and fauna. I want to convert to reconstituted RO water...

I have 7month old 15g column that i started with my liquid rock tap water. I'm using the Tom Barr non co2 method so I only top off with RO water...

Currently the parameters are Gh27, Kh7 and ph of 8.0-8.2

Other tanks using the same water but use aquasoil have very different parameters and grow many more kinds of plants than this one with flourite black sand. ..

My CPDs, pseudomugil furcatus and amano shrimp don't seem to mind, but many easy plants just don't seem to prosper... RCS never berried until moved to another tank (lots of babies now!)

Long story short, I would like to bring the parameters down without causing osmotic shock to the fauna and I've searched with no avail.

Help?
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post #2 of 9 (permalink) Old 09-30-2014, 03:59 PM
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Small partial WCs.
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post #3 of 9 (permalink) Old 09-30-2014, 04:19 PM Thread Starter
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I figured that was the best way, at least as far as fauna is concerned, but I'm not sure how constant water changes will affect my plants as I have prescribed to the non co2 method where the plants adapt to a different source of carbon than what is normally supplied by water changes.

But i suppose over time my plants will adapt again once I get the parameters in order. Currently the hygrophila corymbosa 'angustifolia' has been the only stem that has thrived, while Singapore moss and 8 species of crypts have done well, although the sprialis, retrospiralis and balansae have not faired as well as I thought it would...
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post #4 of 9 (permalink) Old 09-30-2014, 04:29 PM Thread Starter
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Quote:
Originally Posted by Solcielo lawrencia View Post
Small partial WCs.

So if I wanted to reduce my gh to a more reasonable level, let's say 13, how many water changes and how big would they be?

If using straight RO water can I just divide the 50% total water change over time into let's say 10% changes over 5 weeks?

Of course I would need to maintain the kh so the ph doesn't crash...
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post #5 of 9 (permalink) Old 09-30-2014, 05:18 PM
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The math isn't quite right because each 10% is a WC from the total volume that you replaced with RO. So the following WCs are actually less.
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post #6 of 9 (permalink) Old 09-30-2014, 05:54 PM Thread Starter
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Quote:
Originally Posted by Solcielo lawrencia View Post
The math isn't quite right because each 10% is a WC from the total volume that you replaced with RO. So the following WCs are actually less.
Yes you're right

So if I do the math then, I think over 7 water changes of 10% I can reduce gh to just under 14...

But can I safely increase the amount changed and the frequency? Let's say 15% twice a week?

What's your definition of small water changes?

Last edited by hitmanx; 09-30-2014 at 05:55 PM. Reason: spelling
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post #7 of 9 (permalink) Old 09-30-2014, 06:58 PM
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I think I would assume that a 10% drop in GH and KH would not adversely affect the fish or plants, since rain can do that in nature. Based on that I would do roughly 10% water changes a few days apart, measuring the GH and KH after each. I would continue until the hardness was where I wanted it. Those small water changes won't introduce enough CO2 to cause any problems.

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post #8 of 9 (permalink) Old 10-01-2014, 03:16 PM Thread Starter
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Yeah hoppy, that does sound like a good plan.

Thanks for everyone's input... I'll start with small changes and hope for the best...
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post #9 of 9 (permalink) Old 10-08-2014, 04:15 PM Thread Starter
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I have done two PWC of 10% and so far so good... the fish seem fine and plants don't seem to be in distress... Although I added about 25 to 30 more stems stems of hygrophila angustifolia, 3 trident java ferns and added more moss to the branch wood (I'm not sure I like that last change)

The small amount of BBA on the driftwood probably from changing the light bulb, hasn't changed much... Btw what's the best way to manually remove BBA without spreading it?

Gh: 21 (was 27)
Kh: 5 (was 7 and started with 17 from tap)
Ph: 7.8 (was 8.2)

I may need to add some baking soda to up the kh as the last thing I want is a ph crash
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