Monday,23 July 2018, 9 : 23 AM

How to make Water Soft

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Symphysodon spp.:Discus
Image Credit: Hayath M

Introduction



There are situations when we want to make our aquarium water soft and lower our pH.
One of best ways to achieve this is to is to mix RO water in aquariums.
RO refers to Reverse Osmosis filters, which gives you nearly pure water having Gh=0 Kh=0, however most filters have a range so choose a filter to suit your source water.

Pure RO water should never be used in aquariums.
This is due to the fact that it has KH=0 which means that there is no buffering capacity in this water and ph swings are very wild.

Following is the process I followed in my aquarium for altering parameters of my aquarium.
The First Step is to collect information on water parameters.

This is a sample of my aquarium parameters.
Tank Volume =170 lit.
Tank water GH = 600 ppm.
Tap water Gh = 600 ppm.
RO water GH= 50 ppm ( might be lower depending upon your RO system)
Target GH = 340 ppm or 19 gh.
Water Change Frequency = weekly
Water Change % = 50 %

This process has to done slowly so that fish are not stressed and do not suffer due to change in water parameters.
I change 50% of water every week or 85 liters.
My target Gh is 340 ppm or 19 gh.
As stated above I intend to change 85 lit (50%)of water every week.
To achieve my target out of this 85 lit, I use 40 lit of RO water and balance 45 lit of tap water.

This means my 85 liter of new water has a GH of which is calculated as below,
( RO water volume X RO water hardness) +(Tap water volume X tap water hardness).
Divide this by 85.
So you get [(40 X 50) + ( 45 X 600) ] / 85 = 341 ppm or 19.07 dh.

To understand it better let us take it week by Week.

  • Week 1
    At the start of the week my aquarium has water with a GH of 600 ppm.
    Now I take out 85 lit of water.
    I refill the aquarium using 40 liter of RO water and 45 Lit re of tap water.
    This new water has a GH of 341 as calculated above.
    At the end of the week my aquarium will have a GH of 470, which is calculated as per below.
    [(85 X 341) + ( 85 X 600) ] / 170 = 470 ppm.

  • Week 2
    At the start of the Second week my aquarium has water with a GH of 470 ppm.
    Now I take out 85 lit of water.
    I refill the aquarium using 40 lit re of RO water and 45 Lit re of tap water.
    This new water has a GH of 341 as calculated above.
    At the end of the week my aquarium will have a GH of 405. , which is calculated as per below.
    [(85 X 341) + ( 85 X 600) ] / 170 = 470 ppm.

This continued on for 9 weeks after which my Gh stabilized at 341 ppm or 19dh, which was my target gh.





Spreadsheet for Calculating Amount of Water to be changed



Total Tank Volume : 170 liters.
Water change % : 50 %.
Water Change volume : 85 liters
RO Water used : 40 liters or 47% of total with Gh = 50 ppm.
Tap water used: 45 liters or 53% of total with Gh = 600 ppm.


Week Start PPM End PPM
1 600 470
2 470 405
3 405 374
4 374 357
5 357 349
6 349 345
7 345 343
8 343 342
9 342 341
10 341 341