Acans all dying
 

We currently have 6 acan colonies of varying sizes. Until a couple of weeks ago we had 3 more but they have all dies, and now some of the remaining colonies are starting to show the same symptoms. It starts with the heads not fully expanding, then progresses rapidly to a stage where each head/polyp has shrunk down to a tiny size in the middle of the 'cup' of skeleton on which they normally sit, then they die. It usually starts with one head and spreads rapidly over a few days to the whole coral. We tried to frag one which was suffering badly but it died regardless. Some of the colonies have algae growing around the edges leftover from a crazy bloom a couple of months ago when a well-meaning relative overfed the tank while we were on holiday. None of the colonies are new, we've not added any new fish/rock/inverts/corals for months. Tank has been running for about 18 months. We did a rescape recently and have since had a pH drop - initially down to 7.4, now at 7.7. Params are alk 180, Ca 500, Mg 1500, NO3 30, PO4 0, NH3 0. Yes the Mg/Ca and alk are high but they are ALWAYS like this. NO3 is usually 5 - don't know why its spiking. Lights are AI primes. Tank is 90G mixed reef set up with SPS, LPS and softies.

pH is still way to low. My acans have always reacted poorly to alkalinty swings as well

We're struggling to raise the ph. I'm loathed to put buffers in as I've read bad things about them but it seems to be a re-cycle and high nitrate causing it not CO2 or low bicarb.... any tips on how to increase it safely?

I believe kalkwasser raises ph but check that

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The rescape may be the reason in the spike of no3. I don’t think no3 at that level would affect acans anyways. Are they the only coral u are having issues with?

It may be some kind of infection that is spreading from acan to acan. May also be something in the tank picking at them, although I think that would be pretty noticeable because they would look like they would be getting eaten

Buffers will raise your alk. Kalk will raise both calcium & alk. What are u doing to maintain your params. If your dosing two part u can replace that with kalk & that may raise your ph a slight amount. Personally, I don’t worry about ph. Ph rarely is a issue & I think most people who think it is a issue for them end up doing more harm then good with buffers. They continually raise alk why only temporarily raises ph.

water changes 10-20 percent every few days. Proper made mix should have pH ~8.2-8.4

pH is not your issue. People are making too many assumptions about pH, what ever way you prepare your salt mix, it will have a pH at about ~7.7 in the room your tank is found. Dot try to chase it, it is more likely that you will spike your alkalinity while trying to correct pH. What ever you do, it will go back to 7.7 in the long run unless you somehow reduce the CO2 going into the tank.

Just curious given the mass of the Earth's atmosphere and CO2 being present at roughly 400 PPM globally where could the additional CO2 be coming from that's causing their problem in that room? Super tight non ventilated room ? Seems like you would need continuous extra CO2 to effect pH that much.

Yeah mostly ventilation issues, most modern buildings are constructed with the heat insulation as a priority which also makes them pretty well sealed.

Also, in doors CO2 levels are always much higher than outdoor CO2. One study found leves change between 550ppm to 1400ppm (https://www.washingtonpost.com/news/...=.8632f5fbfafa). And the main source of CO2 in doors is humans and any other animals. If you have a gas burning furnace, gas burning oven or fireplace, those add to it as well. Most of the pH related entries happen during the winter since people spent more time in doors, windows are closed and furnaces are working. Also atmospheric CO2 levels increase in northern hemisphere winter since land photosynthesis decrease. Keep in mind 400ppm is also average atmospheric CO2 level. Levels can be a lot higher in cities or even higher in a house next to a highway or factory.

For an aquarium anything that is living in the tank and has a net CO2 production are also sources. Unlike ocean we dont have large number of phytoplankton or sea grass or other autotrophs to consume CO2. That is why fuges with macro algea are great ways to control pH.