dKH Hanna Checker Accuracy

[Bubba12]

I have been adding coral to my 150 for the last few weeks, and recently started dosing Ca and Mg. However I haven’t started dosing Alk yet because of my testing results. Today I tested Alk 3 times back to back with a Hanna Checker and got 11.3, 9.9, & 10. It has me nervous because I would assume the my Alk would be going down because of the 30 or so frags I’ve added. Out of curiosity, I tested with API and got 8. I kinda wanna believe that it’s around 10. I should also add that I was originally using reef crystals for salt but have done my last three 35 gallon water changes with instant ocean in an effort to bring the Alk down slowly. Including one yesterday. Any thoughts? I’m very confused.

 

[Peer.Boerner]

Few things. (1) your Hanna results are likely more reliable than API. I’d base my decision on Hanna. (2) home testing, even high end Hanna gear, is less precise than we realize so those results are more similar than not. Your around 10 dKh (3) Alk varies throughout the day and (4) Alk anywhere around 10 is great! I think you’re in great shape or certainly good shape. I’d leave it alone and wait a week to let things settle down. You can then make small dosing or alk adjustments as you think best. Let us know how things go as you move forward.

 

[Bubba12]

I was under the assumption my Alk should ideally be between 8-9. Is that not correct? If so should I consider a different salt mix? This is an LPS tank so I’m not overly concerned with some minor swings, but my next project is an SPS tank and I want to make sure I have this down before I dive in.

 

[fishface NJ]

Your Alk can be any where between 7 - 11. That is all up to you to decide. Just keep your tank stable. If my NO3 and PO4 is always low I keep my Kh around 7-8

 

[Peer.Boerner]

Alk indirectly measures the amount of bicarbonate that’s in the water. Your coral needs that, along with Calcium to grow its skeleton. Given the inaccuracy of even the best home test kits, experts suggest 9 is an ideal Alk level to promote growth. Regarding salt, what you’ll see at the end of the day is that they’re all good, though some mix faster, leave less residue, can be stored longer, have extra this or that. Success in the hobby comes from diligence watching, but not chasing, the water parameters, observing the coral, and adjusting light, flow, and chemistry as the tank demands. You’re off to a good start. I wish you all the best.

 

[areefer01]

Today I tested Alk 3 times back to back with a Hanna Checker and got 11.3, 9.9, & 10.

I'm not sure how you are testing but 11.3 is the anomaly and is tossed. 9.9 and 10 what you keep.

I do not typically run manual tests but that is because I have automation. However, when I run manual tests to calibrate I will collect a pint of water from the sump where the sample line pulls from. This way everyone is using the same water. Both manual and automation calibration routines. Hopefully you are pulling a pint and running all your tests using that water vs test, walk to tank, pull sample, rinse, repeat.

As far as manual test kits, which are better or more precise hard to say. We sort of all have our favorites but something test kits for like ammonia, nitrate, or calcium some generally raise to the top and frequently mentioned.

Hanna Alk is typically noted as good or recommended.

 

[Uncle99]

I would test over 7 days at least at the same time.
That will give a better picture of what needs to be done, and, what’s the approx daily useage.

8 9 is just fine, running higher just increases costs.

 

[Randy Holmes-Farley]

How much calcium and magnesium are you adding? If alk is not dropping, those aren’t either.

 

[Bubba12]

Thank you all for the advice. Seems like I need more data over the next couple weeks. Never thought to pull a pint out of the tank for testing. I’ve definitely been filling the test tubes directly in the tank.

 

[areefer01]

Thank you all for the advice. Seems like I need more data over the next couple weeks. Never thought to pull a pint out of the tank for testing. I’ve definitely been filling the test tubes directly in the tank.

It may be excessive on my part but this way everything, and everyone, is using the same water. I was only thinking of the alk series and not your larger question.

RHF above mentioned the bigger Q&A though for when you have a spell.

 

[Bubba12]

Im using Nyos 2 part dosing. Ca/Mg and Alk/pH. I’m adding 30ml a day over a 10 hour timeframe. Today Ca was 432 and Mg was 1440. Prior to dosing last week Ca was 380 and Mg was 1340. This is kind of why I’m confused. I assumed my Alk would be dropping too. Maybe I shouldn’t be dosing at all?

 

[Randy Holmes-Farley]

I'd stop dosing for now. The changes may just be random test variation or a salinity change.

The magnesium jump is either a substantial salinity change, or more likely test error. Magnesium testing is not accurate enough to dose based on it. I recommend dosing magnesium based on calcium dosing:

Just say NO to magnesium testing: RMM is born

OK, this thread has been many years in the making, and I'm posting it here since folks in the chem forum are probably already tired of all the threads relating to problematic magnesium testing. I'm going to propose a method, let's call it the Randy Magnesium Method, or RMM for short. All good...

www.reef2reef.com

 

[X-37B]

When I get an odd reading like you did using Hanna I retest. The 13 alk was probably a test error since the other 2 were close.
I use Salifert to cross check when I get a weird reading like you did.

Note: I have over the last several months had a few bottles that were off by almost 1 dkh testing multiple times. I pulled another bottle and it was normal.
No way to tell unless you have another way to measure.

 

[Bubba12]

I tested again today and got:
dKh 10.1
Ca 420
Mg 1360

 

[Randy Holmes-Farley]

I tested again today and got:
dKh 10.1
Ca 420
Mg 1360

All of those are fine. Continue to hold off dosing.

 

[Bubba12]

I tested again today and got:
dKh 10.1
Ca 420
Mg 1360

All of those are fine. Continue to hold off dosing.

Thank you