Test kit accuracy and chasing numbers

[srad750c]

I’ve heard the same issues about Hanna calcium and alkalinity so I didn’t buy them for that reason. Since Red Sea was spot on with Salifert, I’d say you go with that number given the known Hanna issues. I’ve been using Red Sea Calcium with a calcium level maintained at 450 and have coralline growing, SPS Acro growth so I think your good with Red Sea numbers.

As for the Hanna Phosphorus vs Red Sea PO4, a difference of .05 is a lot really. If your target is, say .02-.03 and your test kits are different by .05, then you really don’t know what your PO4 levels are. I’ve done a few comparisons and once they matched but usually Red Sea reports higher PO4. Probably test error on my part the time they were about matched. Hmmm...hobby test kits...

The Hanna vs RSP 0.05 ppm PO4 variance is good enough for me, until now I always thought my PO4 was 0.0 ppm. Not going to use RSP anymore. Turns out my 2 day average is 0.108 ppm and everything does extremely good. Everything in my tank is thriving at my existing chemistry, so I will just maintain it at those levels. Although I will knock that PO4 down to lower level slowly. Not sure how my corals will like the change.

 

[srad750c]

Just a little side bar on testers. I would suggest having a 2 different manufacturers tester for what you are testing. Let me elaborate. I have been mixing my salt using a Milwaukee MA887 to check the salinity. Well I neglected to calibrate for a while and though that my new salt mixes were good to go at 1.025. Yesterday I upgraded from the Apex Classic to the Apex. After getting everything set and the COND probe in the water I got a reading of 43.8ppt which convert to 1.0331 SG. First thought was no way that is right. Then I thought ok calibrate the MA887 and test again and it definitely was correct on the Apex.

I freaked and started taking out water and adding in fresh RO/DI and adjusting the MAG/ALK/CAL as well. I ended up having to replace almost 40 gallons of water to get the salinity down to 1.0286 and will bring it down to 1.026 today.

Now my issue definitely could have easily been remedied IF I was calibrating every time before checking the salinity of fresh salt mixes. Yes I did loose coral and didn't know where to look after everything was SUPPOSEDLY in range.

If my PM2 didn't crash and burn on me and I didn't put in the Apex, I likely would have gone on thinking that everything was ok and that the coral lost was just simply I could not keep that particular coral in my display.

Moral to this story (at least for me) is to never again trust a single source for anything that I am measuring that will be supplemented or added to my display that REQUIRES a particular value. I personally cannot wait for the Apex Trident to come out so I can use it as my primary and my test kits as backup.

I use old school SeaTest hydrometer, 1.025 SG never failed, checked against my ReaSea refractometer and at LFS with their refractometer. Good enough for me.