# Parameter math

424 Views 3 Replies 3 Participants Last post by  lochaber
So I'm trying to reduce the quantity of my water changes in order to reduce shrimp stress. I currently do 50% weekly, but I don't believe there is a need.
I add GH booster and baking soda to meet parameters.

So:
I'm changing 25% of water starting with a GH of 8 and a Kh of 2.
The new water would need 2 degrees GH and 0.5 degrees Kh to keep the parameters stable, right?

(25% of 8 is 2, 25% of 2 is 0.5)

Just looking for someone to confirm my though process. Thanks!

ALSO: should I get a TDS meter to determine when I need to do this water change or just do it weekly? I could test nitrates weekly but wouldn't a TDS account for that?

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If you take 1/2 your water out at GH8 and replace it with water that is GH 0, you will end up with GH 4, because 1/2 of your calcium left with the old water and you did not add any more in.

If you take 1/2 your water out at GH8, and put GH 8 water back in, your GH will stay at GH 8.

if you change 25% of your water. starting GH = 8 if you add water with GH = 0 you will end up with water of GH = 6.

.75*8 + .25*0 = 6
Thanks. So I need to make the new water at a GH 8 and a Kh 2 to maintain stable parameters.

.75*8 + .25*8 = 8
Almost all of the parameters we measure are measured in ratios (ppm=parts per million).

So you want the water you are adding to have the same parameters as what you want the tank to be.

If it helps, try thinking of mixing drinks or something - If you pour a glass half full of 80 proof vodka, and then add another couple shots of 80 proof, everything in the cup is still 80 proof. That won't change unless you add water or something to dilute it.
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