Help me understand my params!

[lpsouth1978]

Please help me understand what is going on here. I recently set up a 40b after a short hiatus and am looking to do things right. The tank got wet on Feb 7, 2021, but I had been cycling the rock in a brute for a couple months before then. I am at a point where I am starting to add more expensive corals and thought I should check all of my params before they got here.

Here is where things get interesting. I see no signs of coralline growth yet and only have a few LPS corals and nems, but my Alk consumption seems off. Tank inhabitants are:

2 x Clarkii clown
Melanarus Wrasse
Small Tomini Tang (will be moving to a 120)
Green Hammer
Gold Hammer
Octospawn
Duncan
Tiny Hydnophora frag
2 x Haddoni Carpets

My Params (checked a few minutes ago)

pH - 8.0 (Seneye)
Cal - 440 (Red Sea Coral Pro)
Alk - 5.7 (Hanna dkH)
Mag - 1350 (Aqua Forest)
PO4 - 0.10 (Hanna ULR Phosphate)
NO3 - 12 (Nyos)
SG - 1.026 (Milwaukee digital refractometer)
Temp - 78.1 (Seneye and Inkbird)

I don't understand how my Alk is so low. I do weekly 20% water changes and my fresh saltwater was 8.0 Alk when I tested it today. Based on the cal and mag, the Alk should be considerably higher, shouldn't it? I have set up my doser to slowly dose a weak baked baking soda solution to slowly bring alk up over a couple days, but I would like to understand what is going on.

Please help. I have added a pic from earlier today so you can see that things seem happy and healthy and everything is open and extended.

 

[Red_Beard]

I had a similar oddity when getting my 75 going. Alk consumption was like 1 dKH a week with zoas in it. I have no idea what caused it either, the only possibility that entered my mind was that somehow the rock was sucking it up somehow. Now, with much more coral a few of which are acro's (still small) the alk consumption is only .3 dKH a week. Thinking back, I think I had to dose it up for at least a month before stuff started being stable.
Hopefully someone has a reason, but at least now you know you aren't alone...

***Awesome Haddoni's BTW

 

[Cory]

Those corals can easily drop alk that quickly. How much alk did you add to your "weak alk solution"? Also rising no3 produces acid which lowers alk.

 

[lpsouth1978]

Those corals can easily drop alk that quickly. How much alk did you add to your "weak alk solution"?

I just added 4tsp of baked baking soda to 1g of RODI. I set the doser to 24 x doses/day of 39ml, meaning it will take 4 days to dose the entire gallon. Using Randy's Reef Calculator, this would be enough to raise the Alk to 11 if there was ZERO consumption. I will test again tomorrow (after 24 doses) and see where it stands. Once I get the system back up to 8.0 I will stop the doser and measure my consumption to set up dosing using Randy's recipe #1.

I am just surprised that a few corals added just a couple weeks ago would be consuming so much Alk already, while Cal and Mg seem unaffected.