Best time of day to test

[van7271]

Values fluctuate throughout the day. The key is to be consistent with the time of day you test.

 

[chipmunkofdoom2]

Well my update is that I can’t seem to get my alk to lower. It’s at 8.9 and I’m still not dosing. I did a 30% WC yesterday and tested today. CA is 430. Why does my alk seem to go up or at least not go down?

If your alkalinity is going up and you're not dosing, the only possible explanation is that your salt mix has higher alkalinity than your tank. When you perform a water change, it's as if you're dosing a weak alkalinity supplement.

If your alkalinity is not going down and you're not dosing, two things could be happening. Either the carbonate alkalinity you're adding with your water changes is high enough that it keeps up with coral demand and abiotic precipitation, or you don't have much demand for alkalinity and what little bit of carbonate alkalinity is in your salt mix is keeping your alkalinity up.

It sounds like your tank has very little demand for alkalinity and calcium, especially if you're only dosing a few mL of supplement every few days. I would not dose anything until you get a better handle on what your tank's chemistry does under normal circumstances. Alk = 8.9 dKh and Ca = 430 ppm are both fine levels and do not require any adjustment.

 

[a-mused]

...finally, someone mentioned Mg. Ca and CaCO3 uptake is facilitated by Mg. If you're not testing your Mg level, start doing so. There's a balance that needs to be struck between Ca, CaCO3, and Mg in order for the Ca and CaCO3 to be efficiently utilized by any coral with a calcified skeleton. Based on your figures above, you should be aiming for a Mg reading around 1350 (that said, still read Farley's articles to understand the relationship and roughly where your Mg should be). Don't use Mg to try and control algae - that's a fool's errand. Test and correct your NO3 and PO4 levels to the point where they're roughly in the proper range based on the Redfield Ratio and the algae should resolve itself over time.

While it wasn't asked, I do find the Salifert magnesium test kit to be both easy and sufficiently accurate.

 

[Ash321]

Isnt it always best to test when the natural daylight is good ? Synthetic light makes testing a nightmare in my house. Obviously better this time of year

 

[ReefersDelite]

I did a test after 5 days of no dosing at all and my calc only went down from 430 to 425 and what’s even crazier is my alk went from 8.9 to 9.3. Why is this happening?

 

[Randy Holmes-Farley Verified Community Expert]

I did a test after 5 days of no dosing at all and my calc only went down from 430 to 425 and what’s even crazier is my alk went from 8.9 to 9.3. Why is this happening?

Both are very small changes, hardly discernable with most kits. Might be test error, nitrate declining, water changes with a higher alk mix, or from artificial rock that is not fully cured, or top off water (like tap) that contains some alkalinity, or salinity changes due to evaporation.

My bet is the values are essentially unchanged.