Need Help to lower ALK its to high like 16

[Jeff Hollabaugh]

Need help have tried it all changed salt mix to a lower alk checked the alk before a water change all three buckets are 8 alk once in the tank its back up to 16 nothing works vinegar works for a very short time has been about 2 years 120 gal tank all other parameters are fine everyone seems happy but i cant keep sps they all die just trying to make the alk stable

 

[BestMomEver]

What is calcium level?

 

[arking_mark]

Need help have tried it all changed salt mix to a lower alk checked the alk before a water change all three buckets are 8 alk once in the tank its back up to 16 nothing works vinegar works for a very short time has been about 2 years 120 gal tank all other parameters are fine everyone seems happy but i cant keep sps they all die just trying to make the alk stable

Just thinking about this from a chemistry perspective and assuming your measurements are correct.

The only thing I can think of that would boost Alk is if your Calcium Carbonate (sand/rock/coral) is dissolving. It would take a very low pH for this to happen.

Otherwise, a 16 dKH with enough Ca will usually result in a precipitation even that will lower Alk/Ca.

Water changes are very good at lowering Alk. However, you will need several larger water changes to achieve your desired Alk which is best done over several days/weeks.

Let's say you do 6 x 20gal water changes on your 120 with 8dKH ASW. You resulting water will only drop 30% from 16 to 11.2dKH.

 

[Roca1357]

Going by above, would you have a pH reading? However, in that situy would you not also end up with readable higher calcium?

When you say back up to 16, does that means you measure a little bit after adding new water and then again later to see levels climb up again?

 

[Jeff Hollabaugh]

Thanks much all my calcium is about 450 and I do 10% water changes every two weeks ph is about 7.8

 

[JGT]

Adding small amounts of white vinegar will also bring your ph down.

 

[Jeff Hollabaugh]

Ok just tested everything after doing a water change on sat with tested alk of 8 alk is back up calcium is 500
Mag 1150 and ph is 7.96 I just dont get it i have tried the vinegar thing but it only lasts a short time i just cant get these parameters stable gonna do the water change thing and I have suffered from low ph in the past

 

[arking_mark]

Assuming your measurements are accurate (they may not be). Try this experiment. Mix 1gal of your new 8dKH ASW with 1gal of your tank 16dKH tank water and measure the new dKH. It should measure 12 dKH.

Then do a single 30gal water change and your tank should drop from 16 to 14dKH.

If instead you do 3 x 10gal water change then your tank should be at 14.2dKH after the change.

Also, how are you measuring dKH and Ca? What testers are you using?

 

[Jeff Hollabaugh]

I will do that thanks am using hanna and seifert

 

[Jeff Hollabaugh]

well I did the bucket thing that

arking_mark suggested and it works the alk was 14.2 so it did go down but then i did a 20 gal water change anf the alk is the same as before but i did test it after about only an hour gonna test again tommorow and do another 20 gal water change on sat​

 

[Randy Holmes-Farley Verified Community Expert]

What salt mix?

You need to test the alk on your new salt water.

If it is 15 dKH+, either it is too saline, a mis-measurement, or a bad batch of salt.

Vinegar is NOT ever a good solution for lowering alkalinity.