Alkalinity keeps dropping despite more than doubling All-For-Reef dosing

[Rick's Reefing Adventures]

Over the past two months, I’ve had to steadily increase my liquid All-For-Reef dosing because my alkalinity continues to decline.

I started at approximately 8 dKH while dosing 4 ml per day. The alkalinity then dropped to 7 dKH fairly quickly, so I increased the dose. It subsequently fell to 6.8 dKH, then to 6.5 dKH, and has now reached 6.1 dKH. Each time, I increased the dose in response to the decline.

Over roughly two months, my daily dose has increased from 4 ml to 8.5 ml. I have just raised it again to 9.5 ml, so I do not yet know what effect that change will have.

I haven’t added any new corals or other livestock in the past few months. The corals currently in the tank, however, have been showing exceptionally strong growth—almost visibly noticeable from day to day. I’ve also added three pictures showing their growth progress over the last three months. This makes me wonder whether their increased growth and consumption could be driving the rising alkalinity demand.

Additional information:

• Tank: 90 L / 25 G, SPS/Acropora dominated
• Dosing: Tropic Marin liquid All-For-Reef
• Alkalinity testing: Hanna Checker
• Dosing pump: calibrated last week
• All of my SPS have been growing noticeably, with growth almost daily

I understand that growing SPS corals consume more alkalinity, but is it normal for consumption to increase this much over such a short period?

Could the increased growth of the corals already in the tank explain this trend, or should I be investigating another cause?
Flow/lights havn’t changed.

 

[EnterName]

I would start by double checking the test. I know that the Hanna reagent can "expire" after being opened a lot faster than the actual expiration date suggests. Keeping it sealed air-tight and shaking it before use apparently helps a bit, but I haven't verified it myself.

Salifert offers a cheap alkalinity test that is titration-based so it offers very good accuracy for our purposes.

 

[exnisstech]

Depending on the amount and size of coral demand can increase pretty quickly IME. My AFR has gone from 20ml a day to 50ml in 3 months to keep it stable at 8ish dkH on my SPS tank after moving to a new tank.

 

[Randy Holmes-Farley Verified Community Expert]

The explanation is the addition started very low and is still low. It is only 0.5 dKH per day. Very low even if rising.

Dose more

 

[Naturalreef]

Just a friendly reminder if you see all for reef not maintaining your alk, check your dosing line to make sure it’s not blocked. I have to clear the line once a week.