Water Changes Affect on Desired Alk

Marquiseo · Dec 15, 2015

Hello,

I currently keep my dkH at 7.5-8.0. I currently have my tank on Automatic WCs in the amount of 20% weekly(divided up daily small changes) via my Kore 5th doser. I am wondering would a higher dkH salt mix drastically affect my desired parameter? I am currently using Red Sea Blue Bucket. I am considering changes back to Pro or another high dkH salt. My tank's total water volume is ~50g.

Downbeach · Dec 15, 2015

If your current method is keeping those numbers, i.e. Alk @ 7.5 to 8 dKH, then I would think that if you were to start using a salt mix with elevated elements, then in some time the numbers would start to reflect those elevated numbers. Although I don't know what your other numbers are currently, i.e. Ca and Mg, there's nothing wrong with an alk @ 7.5 to 8 dKH.

Marquiseo · Dec 15, 2015

Downbeach said:
If your current method is keeping those numbers, i.e. Alk @ 7.5 to 8 dKH, then I would think that if you were to start using a salt mix with elevated elements, then in some time the numbers would start to reflect those elevated numbers. Although I don't know what your other numbers are currently, i.e. Ca and Mg, there's nothing wrong with an alk @ 7.5 to 8 dKH.

I am just trying to get confirmation on my assumption. The dkH is my only concern when it comes to the topoff from the WC. The main reason is that I have half a bucket left of the Red Sea Coral Pro and it is easier for me to obtain that bucket compared to the blue. I don't solely rely on WC for replenishing parameters, I also dose 20mL of Ca and Alk daily.

Randy Holmes-Farley · Dec 15, 2015

The alk will only rise if either you have very little demand in the tank for calcium and alkalinity, or if you keep dosing the exact amount to meet that demand despite the salt mix adding some.

Over a week with zero demand by corals and such, and using the Red Sea salt mix at 35 ppt (sg = 1.0264, alk a bit over 10 dKH), the alk would rise from 7.5 dKH to 8.1 dKH. So it is only adding 0.6 dKH per week. Most people add more than that every day in a typical reef tank.

FWIW, 20% weekly is a pretty large amount of water to changes. Why so large?

Marquiseo · Dec 15, 2015

Randy Holmes-Farley said:
The alk will only rise if either you have very little demand in the tank for calcium and alkalinity, or if you keep dosing the exact amount to meet that demand despite the salt mix adding some.

Over a week with zero demand by corals and such, and using the Red Sea salt mix at 35 ppt (sg = 1.0264, alk a bit over 10 dKH), the alk would rise from 7.5 dKH to 8.1 dKH. So it is only adding 0.6 dKH per week. Most people add more than that every day in a typical reef tank.

FWIW, 20% weekly is a pretty large amount of water to changes. Why so large?

Thanks Randy! I do 20% because I feed a lot and I have seen a reduction in algae (not eaten by my yellow tang). So pretty much I just kept it at that amount. The WCs are 24 cycles a day/ 168 a week in small increments.