Can water changes affect overall alkalinity?

[ridetheducati]

The following formula can assist you in determining how water changes can affect overall alkalinity.

 

Example for 10% water change: (90 * x) + (10 * y) /100 = z

 

X = alkalinity of display tank (dkh)

Y = alkalinity of new salt water (dkh)

Z = new alkalinity of display tank (dkh)

 

10% water change on a tank of 8 dkh with salt of 12dkh

 

(90 * 8) + (10 * 12) /100 = 840

(720) + (120) /100 = 8.4

 

The water change caused the alk to rise from 8 dkh to 8.4 dkh.

Edited April 2, 2013 by ridetheducati

[Jason Rhoads]

When you adjust the % water changed do you simply change the coefficients for x and y?

[Huly]

From one thing we saw depending on what salt is used to mix SW can affect your Alk as some salt is higher ALK and Calc than others

[Chad]

When you adjust the % water changed do you simply change the coefficients for x and y?

 

Yes, just make sure the two coefficients add up to 100.

[ridetheducati]

From one thing we saw depending on what salt is used to mix SW can affect your Alk as some salt is higher ALK and Calc than others

 

The question was rhetorical. I posted the thread to help hobbyist understand the affects. Thanks.

[ridetheducati]

Yes, just make sure the two coefficients add up to 100.

 

Thanks Chad.

 

Example for a 25% water change: (75 * x) + (25 * y) /100 = z

[howaboutme]

Is this formula suppose to supplant actual testing?

 

From what I understand, it's important to know what you're tank is using up from wc to wc. I guess this formula helps us understand those numbers.

 

Are you saying that w/ this formula, forget checking your DT water after your wc since we can just calculate it?

[Marc Weaver]

I think he was just trying to show everyone that at regular 10% water changes alk is not affected as much as you may think. His example was at the opposite ends of the usual ranges. I would not use this formula in place of testing, though.

 

It all depends on the sensitivity of the animals you are keeping. For example, in a full blown, ultra-low nutrient SPS tank with a normal alk of 7.5, I would not do a 20% water change with 12dKH water. That may cause a shock. But for fish/soft coral/LPS I am willing to bet that a 1/2 to 1 dKH immediate change would not cause any problems (other that pissing the coral off for a little while.)

[ridetheducati]

Is this formula suppose to supplant actual testing?

 

From what I understand, it's important to know what you're tank is using up from wc to wc. I guess this formula helps us understand those numbers.

 

Are you saying that w/ this formula, forget checking your DT water after your wc since we can just calculate it?

 

Continue to perform your tests, the formula is not to replace your normal procedures, just another point of reference. Also, it has nothing to do with mineral consumption rates. If you maintain your alk at 10 dkh and your salt mixes to 10 dkh, the formula may not be useful. However, if you maintain your tank at 8 dkh and your salt mixes to 10 dkh, then the formula will be useful. Especially if a large emergency water change is needed.

[PotomacBoater]

You really wouldn't know what X is without testing

(the display)

 

Ride,

for your next trick

I want to see

(#clams * a') + (#lps * b') = monthly calcium/alkalinity usage

 

I know its not that really calculable, but we can dream!

[howaboutme]

I think he was just trying to show everyone that at regular 10% water changes alk is not affected as much as you may think. His example was at the opposite ends of the usual ranges. I would not use this formula in place of testing, though.

 

It all depends on the sensitivity of the animals you are keeping. For example, in a full blown, ultra-low nutrient SPS tank with a normal alk of 7.5, I would not do a 20% water change with 12dKH water. That may cause a shock. But for fish/soft coral/LPS I am willing to bet that a 1/2 to 1 dKH immediate change would not cause any problems (other that pissing the coral off for a little while.)

 

Thanks! This extra context is helpful. To expand upon your last paragraph, this is why dosing is important, right? A little bit at a time so the corals won't be pissed?

 

Continue to perform your tests, the formula is not to replace your normal procedures, just another point of reference. Also, it has nothing to do with mineral consumption rates. If you maintain your alk at 10 dkh and your salt mixes to 10 dkh, the formula may not be useful. However, if you maintain your tank at 8 dkh and your salt mixes to 10 dkh, then the formula will be useful. Especially if a large emergency water change is needed.

 

Thanks for the elaboration!

 

So this as a quick guide to know whether or not the water change will affect your params in a noticeable way. If your Alk low, this calc can be a quick guide to let you know whether or not you will make a dent. If not, then finding an added solution would have to be explored....???

[Marc Weaver]

Thanks! This extra context is helpful. To expand upon your last paragraph, this is why dosing is important, right? A little bit at a time so the corals won't be pissed?

 

I used to dose bulk reef supply soda ash and calcium once a day by hand and never noticed anything bad happening. I was up to 75 mL of each in a 220 gallon SPS dominant and just poured them in the sump slowly 1/2 hour apart. I then started using a dosing pump and dosing a few mL once an hour all day long when demand got higher. The dosing pump controller I have is one where you just tell it how much you want to dose per day and how many times a day and it takes care of the rest. I use a calcium reactor now and will never look back, but that is beside the point....

 

I wouldn't worry about upsetting the coral by manually dosing all of it at a time at first, but once your reef shows lots of demand it will become a pain. It all depends on how much alk demand you have every day. You want to try and avoid a roller coaster type fluctuation of your basic parameters whenever possible. The last time I checked my 220 (which was a long time ago) my reef was using around 1/3 dKH of alk a day. My current tank is still young and when the calcium reactor failed (due to my mistake) I lost .7 dKH in 1 day.

[smallreef]

Ahhhhhhhh I feel like I'm in calc class.....noooooo

I didn't even get past the 3rd line without my head starting to hurt.....

[Marc Weaver]

I know after re-reading it I can picture Ben Stein reading it and saying "anyone, anyone?"