Alkalinity dropped 1.24 while on vacation

[jwshiver]

I try to check my alkalinity daily to maintain it around 7.5. I added two additional pumps to my tank about two months ago to increase flow. In that time I have had to more than double my two part dosing due to increased growth and the addition of a few more SPS. For several months I was dosing 22 ml per day before the addition of the extra pumps, to 45 ml per day before vacation. My alkalinity is now somewhat stable currently dosing 50 ml per day. When I went on vacation I tried not to worry about alkalinity swings due to the steady need to raise two part. Easier said than done. I have had very bad outcomes with alkalinity swings and the resulting loss of coral before taking alkalinity stability more seriously. Hence the now daily checking. When I left for vacation the alkalinity was 7.62 when I came home 7 days later it was 6.38 a drop of 1.24. There is no way to tell how fast it dropped or how long it stayed at 6.38. Needless to say my SPS are not happy! Over the course of 48 hours I slowly raised the alk up to 7.5. Some SPS now have tissue necrosis, poor color and in general don't look happy.

Is the damage a result of the alk drop or is 48 hours too fast to raise alk 1.12?
Does such a low swing cause the same results as a high swing?
What is the affect on SPS of a sustained low alkalinity below 7?

I guess I'll wait it out to see how bad the damage is, before deciding to frag healthy pieces off unless someone can recommend a different course of action.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, I don't know if the problem was the low alk, the sudden rise, or something else entirely.

Hard corals won't thrive when alkalinity gets too low, but 6.38 dKH is the level in plenty of parts of the ocean where corals live, so it isn't low enough, by itself, to kill them.

 

[jwshiver]

FWIW, I don't know if the problem was the low alk, the sudden rise, or something else entirely.

Hard corals won't thrive when alkalinity gets too low, but 6.38 dKH is the level in plenty of parts of the ocean where corals live, so it isn't low enough, by itself, to kill them.

Thanks for the info.
BTW this isn't my final draft. Don't know why it reverted to this version when I posted. This version did not show on the preview. Same general info and questions just not as clean as I had on the final draft.

 

[EJReef]

Thanks for the info.
BTW this isn't my final draft. Don't know why it reverted to this version when I posted. This version did not show on the preview. Same general info and questions just not as clean as I had on the final draft.

Did your coral recover?

 

[reefwiser]

The reason that the increased flow caused a rise in the uptake of cal and alk. Is that the increased flow helped lessen the water barrier at the corals outer layer of skin. This layer in nature is thin due to the high flow of the ocean which we will never be able to reproduce in our aquariums. With low flow the corals have a much harder time getting thru this layer to remove the cal and alk elements out of the water that they need to build their skeletons. So as you increase the flow in the tank the layer of water at the skin of the coral thins and they are able to remove more elements from the water.

 

[jwshiver]

Did your coral recover?

Yes the necrosis stopped and everything seems to have stabilized. Thanks for asking.

 

[jwshiver]

The reason that the increased flow caused a rise in the uptake of cal and alk. Is that the increased flow helped lessen the water barrier at the corals outer layer of skin. This layer in nature is thin due to the high flow of the ocean which we will never be able to reproduce in our aquariums. With low flow the corals have a much harder time getting thru this layer to remove the cal and alk elements out of the water that they need to build their skeletons. So as you increase the flow in the tank the layer of water at the skin of the coral thins and they are able to remove more elements from the water.

It was the Dana Riddle MACNA 2016 video that inspired me to add the extra pumps. I have a 120 gallon and was running two MP40's on each end and then added two Gyre XF230's to the back after watching the video. The return pump is a Ecotech Vectra L1 running at 100% with a Sea Swirl.The MP40's are currently at 75% Reef Crest and Nutrient Transport during the day and 60% Lagoon at night. The Gyres are running on the OGC program at 50%. The results in growth over what I had before have been dramatic.