Alkalinity testing result issue

[tundraguy1106]

Ok so I have been trying to dial in my alkalinity over the past few weeks. Unfortunately I keep adding new SPS corals so it’s making thing difficult. The alkalinity test I routinely use is the Hanna. I also purchased a salifert one back in January to check my results.

In January when I tested with both kits my results were 8.3 on the Hanna and .42 or 8.9 on the salifert. GREAT. I felt that was within reason to be accurate. I still chise to daily test with the Hanna.

my tank is a 4x2x2 120 gallon tank with a 36 gallon sump and live rock. My total water volume is approximately 140 gallons.

Now on to yesterday. I’ve been trying to get my alkalinity to be consistent around 7.8-8.0. Since that day in January my alk has dropped a bit (7.4) with the new coral additions so I’ve been playing with my doser to get it adjusted back to my goal range. After testing my alkalinity, which read 7.4 I decided to up my alk doser to 22ml /day. The day before my alk was 7.5 at 20 ml/day.

Nows where it gets interesting. I decided to check my calibration on my doser (kamoer unit). I ran a 20 second check which filled my test cup 15ml. The doser read 43ml!!! WOAH! Ok so I reset it to 15ml and calculated 15ml being 35% of 43ml. So I adjusted my dosing to 35% of 22ml (my current dose) which came to approximately 8ml. I also added an adjustment dose of 7ml which bumped my alk up to 7.6

On to today. I go to test my alk today and of coarse my reagent ran out. I crack open a new bottle and test my alk. I get a reading of 8.4! Not crazy high but definitely off from the day before. I retest and get the same result. I pull out the salifert and I’m getting .33 10.4! Which is high! Now I’m confused because a month ago these tests were within .6 DKH, now they’re off by 2 DKH. I retested with the salifert and got the same result. I noticed minimal polyp extension today on my SPS and wonder if my alk spike caused this. Due to conflicting test results I’m super confused as what to trust. I’m currently mixing a fresh batch of saltwater (tropic Marin pro) and going to test that water and then do a water change. I shut my doser off for the night and will retest tomorrow seeing what the tank uses over night.

I know I set myself up for the perfect storm with the recalibration the doser and then a new reagent but any information or tips to help me out would be great. Don’t wanna lose my corals. Last time I had an alkalinity spike (8.5 to 9.5) my space invader pectinia, a trumpet coral and a few SPS frags all got burnt tips and still haven’t recovered!

my parameters are
Salinity 1.026
Nitrate 5
Phosphate .04
Alk ??????
Calcium 470
Mag 1400

 

[tundraguy1106]

So I just tested the freshly mixed tropic Marin pro saltwater

salinity - 1.025
hanna Alk - 6.9 Dkh
Salifert Alk - .46 8.3

 

[William Morris]

Do you have the Hanna standard's for Alk to see if your checker is calibrated?
Gives me peace of mind to pop those into the checker from time to time.

 

[tundraguy1106]

Do you have the Hanna standard's for Alk to see if your checker is calibrated?
Gives me peace of mind to pop those into the checker from time to time.

I’d have to order them. So if I do and the checker is off then what? Buy a new one?

 

[William Morris]

Not sure how that would work. I don't know if Hanna can calibrate them or if they consider them to be disposable.

 

[elysics]

The problem with the hanna "calibration standards" is that 1. They only check the checkers led and light sensor, not your chemicals or the vials you are actually using for the test, or even your testing procedure, and 2. You can't calibrate the checker even if it is off. Though I don't know whether Hannah's reaction would be to replace it or tell you to buy a new one.

I'd use a normal seawater reference solution and test that, that tells you whether your chemicals and the whole process works, not just the led.

 

[Marc Pardon]

Did you clean your sample cuvettes properly on the outside? I use office cleansing wipes to make sure the glas is clean ..... if I don't do that I have deviations between Hanna and Salifert

 

[tundraguy1106]

Did you clean your sample cuvettes properly on the outside? I use office cleansing wipes to make sure the glas is clean ..... if I don't do that I have deviations

Yup. I rinse with RO or distilled water and wipe the cuvettes before every test. I hold them up to the light to make sure there are no smudges. So I mixed new salt water and did a water change (15 gallons) and retested. Now the tank on the Hanna kit is at 8.2. I left the doser off and I’ll retest later today and see how much I’m down. I researched and found other reefers who had 1.2 - 1.5 discrepancies with the salifert kits.

 

[Deep]

So I just tested the freshly mixed tropic Marin pro saltwater

salinity - 1.025
hanna Alk - 6.9 Dkh
Salifert Alk - .46 8.3

so this seems to suggest that the hanna is correct and salifert is not.

 

[tundraguy1106]

so this seems to suggest that the hanna is correct and salifert is not.

That was my thought too

 

[tundraguy1106]

so this seems to suggest that the hanna is correct and salifert is not.

I just don’t understand how dosing 7 ml of alkalinity raised my tank .8 and that’s with whatever the tank was consuming. According to the alkalinity calculator 7ml on my sized system should only raise the tank by .1?

 

[tundraguy1106]

Update.... so I found the manual for my kamoer doser and it states that the calibration period is 60 seconds. When I cut off the calibration at 20 seconds and then calibrated the pump, it caused the doser to think the calibrated amount for 60 seconds was 15 ml. In actuality, the amount dosed after 60 seconds was 43-45 ml. I updated the amount and then tested it by doing an adjustment dose of 25 ml. Upon completion of the adjustment dose, I had 25ml in my measuring cup. I did this for both pumps, so I believe I fixed the issue. Anyone know how often you should calibrate dosing pumps??? Thanks