Corals RTNed due to low ALK

[kaxt]

I just got home from work and noticed that 2 of my SPS RTNed today. I have a green pocillopora that is 3/4 of the way gone. It is the largest SPS that I have in my tank. I also have a birdsnest that lost at least a half inch of flesh on each tip. I immediately checked my hardness and got a low reading of 5.1 dKH.

I checked my CaRx and it was completely clogged up. I had noticed a huge explosion of growth last week on both of these corals, so the reactor couldn't have been clogged for very long. Even my mother, who is not very observant, commented on the growth when she was over. It surprised me that my alkalinity could have gotten that low that fast.

Anyways, I've done a few searches on what I should be doing now, but I can't really find anything. I've found a lot of information stating that alkalinity swings can cause corals to RTN, but I already knew that. I know I need to dose slowly to get my levels back up, but is there anything else I can do in the short term to save these corals? Or do I just bring my levels back up and hope they recover? I feel like this question has to have been answered before, but I guess in my panic to find answers, I'm just not coming up with the correct key words to search.

Thanks in advance for any advise.

 

[kaxt]

Okay, now I'm completely confused. I just tested calcium and got a reading of 400 ppm. I setup the CaRx a little over a year ago and really haven't tested, or touched the reactor since. I balanced the 3 big parameters before I dialed in the reactor. When I was convinced the reactor was set, Ca was 420, dKH was 8, and Mg was 1325.

I have a DOS pump that changes a gallon of water every day, another pump that doses 6ml of vodka everyday, and the CaRx. The only hands on things I do are clean the skimmer and the glass. If I stared the reactor with balanced parameters, how is my Calcium still at an acceptable level while my alkalinity has plummeted?

 

[Pife]

Your water changes kept up with it.

 

[jda]

I have had alk get that low with no RTN. Most RTN is from more than one source... like organic carbon dosing AND low alk, or low alk and low quality light, etc. This like low quality lighting, carbon dosing and other methods oft only work long-term when everything is perfect... there were less RTN events a decade ago when people only used high quality light, no organic carbon or chemicals/media... there was other problems, but RTN was not as prevalent.

In your case, the explosion of growth probably came from low N and P from the organic carbon dosing, which probably drove the alk lower from the growth and then the stress from these two things caused the issues.

Tank inhabitants do not usually use calcium and carbonate in equal proportion... acros usually do, the coralline, clams and other things do not. Also, unless you doctor your salt mix to match your tank exactly, then changing water can move the needle as well. About twice a year, I need to merry up the calcium and carbonate.

Get the CaRx going again. This needs to happen.

Get your alk and calcium where you want them in your tank - baking soda and dowflake (calcium chloride) will be fine.

Take measure of your salt mix and the parameters. This is why a lot of high-end SPS folks use Instant Ocean... the calcium is low and they can easily raise it and the alk can be easily dropped with Muratic Acid.

 

[kaxt]

I have a 90 gallon DT and a 75 gallon sump so I feel as though my measly little 1 gallon water changes can't be what kept my calcium up. The pocilipora was completely gone by the time I went to bed last night. The birdsnest that I thought was going seems fine today. I think that it just didn't have any PE and that combined with the white tips from all the growth made me think it was in trouble too. The smaller frag of purple pocillopora i have directley next to the dead one seems fine.

I run XR30 G3 pros so I wouldn't consider my lighting to be low quality. Also, I've been dosing vodka for 3 years and my N and P are stable, I didn't have a reduction in nutrients just before the growth explosion. My tank is a mixed reef not just SPS, and while it's not tank of the month material, it has really been thriving until yesterday.

I have my reactor running again and I dosed enough soda ash yesterday to bring my hardness up 1 dKH. I plan to test again and dose again tonight.

All that being said I feel as though I do have something more going on and that I probably posted this thread in the wrong forum. Today my star polyp is all closed up, so are my acans, and a leather, and my 3 BTAs have all moved and look like they are on deaths door. Everything else, including an acro, looks great.

 

[kaxt]

Here are a few pictures of the tank just to give you an idea. I'm sorry that I posted in the SPS section, but originally I thought it was just a stony issue.

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