pH and SPS

cmac330 · Oct 26, 2015

So I have diligently worked to stabilize my tank last year, I increased my water volume, added dosing pumps, ato, run two mp40s on a reeflink for a 48" x 20" x 18". I closely monitored things after the big change and any subsequent changes have happened one at a time and with a least a month in between (so as to eliminate variables in the case of a change in coral health). I started by running my parameters close to NSW values with my alk at 8-8.4 (depending on time of day), calc at 410, and mag at 1300.

I noticed that I was still struggling with certain corals, and in particular montipora capitata and digitata as well as birdsnest. My acropora valida and samoensis were doing great as well as my mystic sunset montipora (don't remember the species) and were all growing while the others continued to struggle. I use tropic marin salt and use their balling method powder in my doser (I know it is a higher price but I like the quality and it keeps my trace elements stable) so all of my parameters were reading at acceptable levels when tested but I noticed my pH never went over 7.9. My wife and I live in a 1200 sq foot apartment with three dogs (one of which is yappy and does not allow us to leave windows open for long).

Noticing my pH issue I did the research and decided to just bump up my alk/calc/mag levels to 10.4/450/1400 to try and offset calcification issues caused by the pH. However, this hasn't seemed to help too much. I notice that from time to time these corals will do better in my tank (only ones I have left are monti caps, got rid of the others or lost them) for a week or so and then will struggle again. During this time I will also notice a significant increase in growth of my stable acropora. After seeing this happen a few times I began to watch more closely and these periods seem to happen when the gas oven/stove was not run for a substantial period of time and/or the windows were not opened for a while. I am starting to believe that pH swings are a significant factor in my issues.

I have also recently noticed that echinata and millepora are two acros I just cannot seem to keep in my tank. Does it stand to reason that certain species would be this much less tolerant of pH? I have tried running limewater but the evaporation doesn't seem to allow me to use enough to offset the pH dips. I have tried running my nitrates at ~10 for a couple of months and then at ~1 for a couple months and saw no difference.

I am considering just avoiding most sps and just sticking with the ones I have, I hate to think it is my only option but I also hate killing coral.

Thanks

redfishbluefish · Oct 26, 2015

I don't think you have a pH problem. I think it's something else.

You didn't mention, but what are you using for lights? And I'm also assuming your nitrates and phosphates are in order.

Randy Holmes-Farley · Oct 26, 2015

It is almost certainly true that some species suffer more from low pH than others, but it is not clear what those sensitive species might be, or how low the pH would need to be to cause problems.

What is the pH low in the AM? pH 7.9 is not low enough to be an big issue for the SPS c0rals you mention, I don'
t think, since many reeef tanks with then drop as low as pH 7.8.

If you are keeping a ULNS (ultra low nutrient) tank, having the alkalinity higher may be more of a problem (from burnt SPS tips) than the lower pH resulting from lower alkalinity would cause.

cmac330 · Oct 27, 2015

My pH is actually rather stable (I assume because of the strong alk level combined with the already high saturation of CO2) and the low is usually 7.7 I don't know if nitrates around 1-5ppm are ULNS with PO4 around .03ppm. My larger concern is that it is the pH swings when we use the gas stove or open the windows.

I have thought about trying out a triton test to make sure the balling liquids haven't oversaturated any of my trace elements, but I feel this is highly unlikely.

Also the die-off on the montis seems to be in random places and is as common in the center as it is on the tips. In fact many are still growing as the center dies-off. My red Montipora cap is the slowest growing coral in my tank, doesn't have die-off but doesn't look great either, after having it for two years, which just makes no sense to me.

Randy Holmes-Farley · Oct 27, 2015

I'd track the pH when you do thing that might drive it lower. At pH 7.7 or below, aragonite (such as coral skeletons) can begin to dissolve, and the farther down you go, the faster it will be.

I'm not sure what might cause die off in the center, aside from shading or lack of water flow reaching the middle of a coral.