How did my alk get so low?

[Clown2020]

So recently noticed a large difference between the alk of reef crystals and my tank, i then posted a thread asking if it was time to start dosing and the consensus was yes and all for reef would be a good product.

However before I start dosing I want to get a better understanding on what is happening with my alk and how I got to this point. I have been testing daily and im averaging 0.3 dkh drop per day. My reef crystals mix to 11.5 dkh at 1.026 salinity and I change 30% each week. My dkh started at 7 after my last water changed and is currently at 6.2 .

My usage over 7 days should be 2.1 dkh and a 30% water change should replenish 30% of the alk am I correct? Which would be 3.5 dkh so my alk should not be dropping?

ca is currently at 425 avg drop 10 and mg currently at 1320 and avg drop 20

i did notice that consumption of ca and mg slows as alk drops.

is there somthing wrong with my math? And should I correct my alk before I start dosing all for reef?

 

[Dennis Cartier]

I would not worry about it too much. Your alk consumption will be greater at higher alk levels and will slow as the alkalinity drops (as you have noticed). This makes it hard to quantify it as xx amount per day, as xx is always changing as your corals speed up and slow down their growth. As soon as you start dosing AFR, the daily decline will be moderated, and you will either see no drop, a gradual drop, or a slow increase, and you can then adjust your dosage based on that. I expect that once you stabilize your alk, even a little, your corals will respond in kind by growing faster, and you will then have to nudge your dose up as they do.

Your calculated drop of 0.3 dKH per day sounds reasonable and I would use that as your daily dose to start. You just need to monitor your alkalinity closely while you gauge how the starting dose is received by your tank and go from there.

Dennis

 

[Dennis Cartier]

Oh, I forget about your question on correcting your alk. Perhaps do a water change first, which will get your alk back above 7, and then start the AFR.

A 'sweet spot' will become apparent where your corals are happy at a particular alk level, and your water changes don't move it too much from that level, and where your AFR daily dose maintains that level. Now you just need to find the level for your tank.

My guess would be that you will evenentually settle on 8.0 - 8.5 dKH.

Dennis

 

[Randy Holmes-Farley]

0.3 dKH per day is on the low side or normal and seems quite reasonable.

At that rate, the magnesium decline will be imperceptible except over many weeks, and the calcium decline is only about 2 ppm per day.

 

[Clown2020]

Thanks for the replies, Will start dosing after my next water change tomorrow.

do I need to be concerned about all for reef potentially causing my ca and mg to rise?or am I starting to overthink things?

 

[Dennis Cartier]

Thanks for the replies, Will start dosing after my next water change tomorrow.

do I need to be concerned about all for reef potentially causing my ca and mg to rise?or am I starting to overthink things?

It may cause your levels to rise if you overshoot the dose, but it should be no problem to dial it in within a few days. Just remember to wait 24 hours after a dose to see the affect of it. The AFR has to be metabolized by bacteria before your levels will reflect the dose.

You may want to dose less than you think you need to (to start), and then work your way up to your preferred level over the course of a week or two.

Dennis