using baked baking soda, KH not raising?

[Surykor]

Hi there,
I have been dosing kalkwasser about month succesfully keeping alkalinity at about 8,5 dKH
About week ago I went to a fish store and bought some DI resin, frozen food and CA test kit just for sure. Measured CA about 550+ so i stopped using kalkwasser for top off water. made a 10% water change, scrubbed and siphoned huge amount of GHA.
last measure Ca was about 510 and KH 7,7 dKH so i added some baked baking soda to top off water using http://reef.diesyst.com/chemcalc/chemcalc.html calculator to get KH back to 8,5 dKH. and here comes the problem.
Right now i used 3x more than recomended dose and KH is still the same 7,7 after 2 days of dripping high alk top off
does anyone have idea why alk is not raising ? thx for replys
info: tests Salifert, 30 galon mixed (few SPS frags, LPS, 1tridacna clam, 4 little fish and shrimp) skimmerless, using clearphos to fight GHA.

 

[Randy Holmes-Farley]

The only reasons could be that you are not adding enough to offset both the ongoing demand as well as the amount needed to raise it (possible), that the kit is bad (unlikely) what you are using isn't baking soda (not very likely, what brand?).

 

[Surykor]

Tried to test twice with 2 different salifert kits with minimal deviation.
using Soda bicarbona NAHCO3 baked 1hour+ at approx.160°C
I quess brand is pointless because Im from Czech
I measured PH and KH of solution.. both off the charts on the high side so Im sure its not baking powder etc. I was little worried with no difference but I will continue and see if KH starts to rise slowly.
I dont wanna use it for long term. just want to raise it and continue with less kalkwasser and more WC. (using RS coral pro salt)

only 1 more thing comes to my mind that can lower KH a little - clearPhos. however I use about 1/2 of recommended amount from LFS
thx in advance

 

[Randy Holmes-Farley]

OK, brand probably is pointless, I just wanted to make sure it wasn't "baking powder". Sodium bicarbonate is the product to use.

Good luck.

 

[hkgar]

Your tank is using it as fast as you are adding it. I run a calcium reactor and when my ALK starts to go down from increase usage (growing SPS) I increase the flow rate to keep up with demand and use the ALK part of Randy's two part to get it up to where it needs to be.

I like my ALK about 9 and yesterday it was 8.4, so I added 1.8 ounces of the ALK part of Randy's yesterday and another 1.8 to day.

 

[Surykor]

Well i have 3 little SPS frags (brown an pale ), 1 clam and 2 lps frags. Do you think they can take so much alk?
This morning I measured alk 8 dKH so I think I will continue to rise it to 8.3-8.5 and try to do my best to keep it there thank you guys for replies

 

[Randy Holmes-Farley]

I'd add whatever baking soda it takes to maintain 7-8 dKH.

 

[Eyore]

precipitating due to high calcium or salinity?

 

[Randy Holmes-Farley]

Yes, higher calcium will increase the abiotic demand, but not nearly so much as pH. A pH rise of 0.3 pH units is equivalent to a doubling of the calcium level with respect to calcium carbonate precipitation.

 

[Surykor]

Salinity is 1,025 now, but dont know what is Ca reading now . Last time i chcked was 500ppm. It should drop slowly to desired level as I dont add any now.

 

[Randy Holmes-Farley]

Sounds good.

Good luck.

 

[tmz]

Measured CA about 550+ so i stopped using kalkwasser for top off water. made a 10% water change, scrubbed and siphoned huge amount of GHA.

Have you checked the newly mixed salt water? Some folks have reported variable levels of calcium and alkalinity with the salt you are using depending on mixing times.


Kalk should not raise calcium and alkalinity disproportionately since it provides a balanced amount of calcium and alkalinity in the proportions used when calcium carbonate is formed.

Elevated pH could be causing abitoic preciptitation but that would use both calcium and alkalinity proportionatley.

 

[Surykor]

Thx for responses well Ph sits at between 7,7 and8 on salifert test. dont think its the problem .however about half year back ph was 7,4-7,7 ( gas exchange was the key ) Maybe salt . Using RS coral pro big 22 kg bucket. Tested new bucket once. Kh was little lower than advertised Maybe around 9 as i remember but not measured Ca. ( no test kit in old days ) .. Will try next time during WC.. I mix salt only 0,5 hour max before WC - untill water is clear