Help understanding alk and pH change

[syntax_error]

Hello all, I need some help to figure this out.

 

Yesterday morning (1hr before lights on) my alk was 8 dkh, pH was 7.8 and Ca was 380 ppm.

I added 5 ml of Kent Tech CB part B (alk)

25 ml of Kent Tech CB part A (Ca)

 

Today morning (about 1.15hrs before lights on) my alk is 7 dkh (tested twice and got the same result), pH is 8.2 and Ca is 400 ppm.

Why did the alk drop by 1 dkh and pH rise by 0.4?

 

Mg - 1230 (salifert Magnesium test kit)

 

pH, Alk and Ca tested with an API test kit.

 

Tank is 29 gallons (but I consider the water volume to be 26 gallons).

It's about an year old tank. Currently no corals. SG - 1.026.

Salt mix is IO reef crystals. New salt water pH - 7.8, alk - 8 dkh, Ca - 380 ppm.

 

Anybody?

[westcoastreefer84]

7-8 is natural sea water, so I don't see a problem

 

Your increased calcium could be to blame for the slight drop in kh

 

OT: kent tech 2 part must be some weak stuff, 5ml of oceans blend cal raises my tanks cal by 25ppm

[TM01]

Your addition of 25ml of calc dropped your Alk. I dont like adding alk, calc or mag at the same time.

 

Concerning your Ph. It can fluctuate at any given time. Its always hard to answer questions on Ph due to variable conditions at the time it was read...But I would suspect it was related to dosing last night.

 

Also..if your running 1.026 and using Reef Crystals. I would think you should be seeing readings higher than this.

[syntax_error]

I don't understand how the calc addition dropped alk. Can you explain please?

 

I expected Reef Crystals to give me higher numbers than this as well. May be it has something to do with the batch.

 

Also, if I am dosing using a balanced two part system, do I have to dose same amounts of part A and B?

Or can I just dose them independently like I've done up to now.

For example I dosed 25ml Ca and 5ml alk. (dosed according to the reef chemistry calculator)

Or do I have to do 5ml Ca and 5ml alk (same amount).

[vangvace]

http://reefkeeping.com/issues/2006-06/rhf/index.php

 

http://www.advancedaquarist.com/issues/may2002/chem.htm

 

see if these 2 links don't answer your question.

 

There is nothing wrong with dosing different amounts of part A and B. Make sure that the first has dissipated before adding the next one.

[westcoastreefer84]

Reef crystals will give you mixed test results, the numbers listed on the bag are only good when the entire bag is mixed at once, I keep my salt in a plastic covered bucket, I shake vigorously before mixing, also if your numbers were off prior to using IORC, they will still be off

 

You should read up on water chemistry, cal, mg, and alk levels are all affected by each other, ph is affected by a whole array of differant things

 

 

As for your 2 part system, you should be testing and dosing only as needed, you should always dose cal first as this will lower kh, then adjust your kh as needed, you don't always have to dose both parts

[syntax_error]

I've read some of the articles on ca and alk, but I don't get why alk goes down when calc is added.

 

As for the relationship between alk and pH - when I add alk the H+ ions binds to CO3 ions resulting in lowering the pH. Is that correct?

[westcoastreefer84]

Adding alk raises your ph, that's why you dose when your lights are off so it doesn't spike your ph

[Mr. Fosi]

Why did the alk drop by 1 dkh and pH rise by 0.4?

 

#1 - Are you sure you are being precise in your titrations?

#2 - If you are using a pH probe, when was it last calibrated?

 

Adding alk raises your ph...

 

Only if you are adding Na₂CO₃ (sodium carbonate or washing soda) (B-Ionic original recipe or Randy's Recipe #1).

 

If you are adding NaHCO₃ (sodium bicarbonate or baking soda), pH goes down just after addition but you also have to add more to get the same impact on your alk.

[syntax_error]

#1 - Are you sure you are being precise in your titrations?

#2 - If you are using a pH probe, when was it last calibrated?

 

 

 

Only if you are adding Na₂CO₃ (sodium carbonate or washing soda) (B-Ionic original recipe or Randy's Recipe #1).

 

If you are adding NaHCO₃ (sodium bicarbonate or baking soda), pH goes down just after addition but you also have to add more to get the same impact on your alk.

 

#1 - I think I'm fairly accurate since I do the titration twice with the same result.

#2 - Not using a pH probe. Using API test kit.

 

I still don's see how alk goes down with increasing calc. m...

[Mr. Fosi]

In many tanks, alk decreases with Ca in a ratio of 2:1.

 

You could be seeing an increase in calcification that was jump-started by the addition of the Ca. Is this is a regular occurrence in your tank or have you only seen this once?

[syntax_error]

I haven't really dosed supplements to this tank that much, so I can't really answer to the question of whether this is frequent in the tank. I'd think this is the first time I'm seeing this because I just started dosing.

 

So this decrease in alk is because of the formation of calcium carbonate, correct? But within a day can there be enough calcification to bring down the alk 1 dkh? (from 8 to 7 with the increase of ca 380 to 400). I do see a lot of Coraline growth though.

 

Speaking of ratios, balanced two part alk and ca supplements are made with that ratio as well correct?

 

sorry, I'm a bit confused in this subject.

[westcoastreefer84]

This may be a long shot but I think its a plausible theory

 

Your tank is obviously a bit unstable, probably because you havn't been keeping your cal, mag and alk levels as consistent as they should be

 

What I think may be happening is, you overdosed your calcium, 25ml on a 29gal tank should have shot you up atleast 100ppm in cal, your mag is already on the lower end, 1350-1500ppm is recommended for a reef tanks, you need mag to keep your calcium from percipitating, so what I think happened was all the cal you dropped in the tank percipitated out causing the kh to lower

 

I am in no way an expert so please correct me if I'm wrong, just another reef nerd trien to give my 2 cents, I've been searching for the past 20 mins about this subject

 

Here's a link that might be helpfull for you to understand dosing

 

http://www.advancedaquarist.com/issues/nov2002/chem.htm

[Mr. Fosi]

So this decrease in alk is because of the formation of calcium carbonate, correct? But within a day can there be enough calcification to bring down the alk 1 dkh?

 

That is my guess, yes.

 

I see a daily drop in my system of at least 1 dKH/day with an average between 1.5 and 2.5 dKH.

 

Speaking of ratios, balanced two part alk and ca supplements are made with that ratio as well correct?

 

They are supposed to be, but the ratio isn't perfect. 2:1 Alk:Ca, like all biological/biochemical ratios, is a rule of thumb and isn't universally true. Most additives claim to be "balanced" but the systems they are added to are often not.

 

Mine is a perfect example. I run through oodles more Mg and Ca than I do Alk but ask Propagator and he'll tell you that he runs though roughly twice the Alk than he does Ca. Everyone's system is different even though they all share similarities, thus dosing is a highly individual thing.

 

Since you aren't sure if this is a regular occurrence, you should replicate your additions over the next couple days/weeks and see if this is a reproducible phenomenon.