P.h. Too Low

[Xler8n]

I just checked my PH this morning and found that it was between 8.0 and 8.1. What should i do?? Can this have a huge affect on my corals and inhabitants in my tank?? I thought that with crushed coral and LR in my tank that would act as a buffer and keep the PH at 8.3 or 8.4. What could be happening?? Oh i was also reading that PH drops at night... I tested my water at about 5am before i went to work. My lights come ON at 4:00pm and go OFF at 12:00am (So i can see my tank when i come home and before i go to bed). My refugium light turns ON at 1:00am and turns OFF at 9:30am. Should i try testing it at another time?? What time would be best?? I think when i tested my PH before it was at about 8.2 is that too low also?? What is the ideal range for a Reef tank.. 8.3 right?

[Fat Tony]

nothing... there is nothing wrong with pH in that range. Many people have pH that is in the 7.8 range. Also, don't worry so much about what your pH is in the morning, test it in the evening at the end of the lighting cycle...it will be higher at the end of the day.

[crvz]

First, I'd ask how you measured pH, and second, I wouldnt do ANYTHING. Too many people get wrapped up in pH numbers, but 99% of the time or more there's no reason to do a single thing about it. Lowered pH may have some slight affect on calcification in stony corals, but if you're anywhere within the 7.8-8.4 range there's not a thing to worry about. Often, when we have company over or if the HVAC system has been off for a while, my pH can dip below 7.6 due to the increased CO2 levels in the house, but never once have I noticed any problem because of it.

[Xler8n]

Ok.. I checked my PH again afetr the lights went off and the colors are between 8.0 and 8.2 so im guessing its at about 8.1. I thought that was too low and that a healthy reef aquarium has a PH of 8.3?? What should i do?? Should i just let it be and not add anything like REEF BUILDER or REEF BUFFER??

[motorslave]

Originally Posted by Xler8n

Ok.. I checked my PH again afetr the lights went off and the colors are between 8.0 and 8.2 so im guessing its at about 8.1. I thought that was too low and that a healthy reef aquarium has a PH of 8.3?? What should i do?? Should i just let it be and not add anything like REEF BUILDER or REEF BUFFER??

Youre fine. Read Chris and Toy's posts above. They covered it.

[kyrie_eleison]

I wouldn't worry about it. Your pH will drop a little when the lights go out. If it's keeping you up at night, you could always dose your tank with kalkwasser. That often helps but do so with caution as it can be somewhat "caustic" and you have to do it slowly. You can also use a "pH buffer"...HOWEVER, the buffer doesn't last. Buffer is only a temporary solution to a long term problem.

Another solution would be to check your kH. That often can be your problem. If your kH is too low, then you don't have the buffering capacity to maintain a stable pH.

Tell us more about your tank parameters. Reef chemistry is critical when you get to into the realms of SPS.

[cronamator]

also when its an excellent time to drip kalk or add your dkh buffers

[tdwyatt]

...or do nothing.

There is nothing wrong with your tank. pH is controlled by the concentration of CO2 in the water, and as there are photoautotrophs* (organisms that use photosynthesis to make carbohydrates and simple amino acids out of CARBON DIOXIDE) in the tank, they will CONSUME CO2 during the time that the light is on, reducing the amount of CO2 and causing the pH to rise to a normal daily high of anywhere from 8.3 to 8.5. This changes when the lights go out, as the photoautotrophs lose the energy(light) that drives photosynthesis, AND THEY BECOME NET CONSUMERS OF THE CARBOHYDRATES THEY MADE DURING THE DAY (CHO's). This means that they "burn" the CHOs for chemical energy and break them down back into CO2, which they dispose of into the water column as a waste product. Increasing CO2 causes DECREASING pH, as low as 7.8 normally depending on how many and how dense the populations of the photoautotrophs are in the water. It is totally normal to see a daily swing in pH on a diurnal scale. As the normal pH of seawater is 8.2-ish depending on what time of day (and the consequential concentration of dissolved CO2 is in the tank water), expect to see a swing from a normal nadir of 7.9 to a peak of 8.4 without consequence to your tank inhabitants. The reason that even with normal levels of alkalinity that this swing occurs is due to the RATE of the changes in the concentration of CO2. The rate of change in CO2 concentration due to photosynthesis is at a greater rate and scale than buffer can compete with, even though it does prevent large swings to extremes based on how much CO2 is produced or removed by the organisms in the water column beyond the extremes of these ranges as new products of the carbonate/bicarbonate buffer system begin to appear with shifts in pH (other factors begin to come into play at these extremes based on degassing of CO2 and solubilization of solid CaCO3 substrates at the extremes). Remember also that we have much more dense populations of these organisms in small closed systems than exist in the scale of oceanic population densities.

Higher concentration of CO2 CAN have unusually effects on buffer capacity and visa versa, best summed up in the following chart:

Ratio pCO2 For ASW compared to NSW
VALUE IN CHART IS COMPARED TO A VALUE OF 1 FOR nsw AT SEALEVEL, OR x:1

Total Alkalinity (AT)
(mEq/l) . . . 2.0 .. 2.5 .. 2.6 .. 3.0 .. 3.5 .. 4.0 .. 4.5 .. 5.0 ... 5.5 ... 6.0
(dKH) . . . . 5.6 .. 7.0 .. 7.3 .. 8.4 .. 9.8 . 11.2 . 12.4 . 14.0 . 15.4 . 16.8
pH __________________________________________________ _________
7.7---------3.0 .. 3.7 .. 3.9 .. 4.5 .. 5.3 .. 6.0 .. 6.8 ... 7.5 ... 8.3 ... 9.1
7.8---------2.3 .. 2.9 .. 3.0 .. 3.5 .. 4.1 .. 4.7 .. 5.3 ... 5.8 ... 6.4 ... 7.O
7.9---------1.8 .. 2.2 .. 2.3 .. 2.7 .. 3.1 .. 3.6 .. 4.0 ... 4.5 ... 5.0 ... 5.4
8.0---------1.3 .. 1.7 .. 1.8 .. 2.0 .. 2.4 .. 2.7 .. 3.1 ... 3.4 ... 3.8 ... 4.1
8.1---------1.0 .. 1.3 .. 1.3 .. 1.6 .. 1.8 .. 2.1 .. 2.3 ... 2.6 ... 2.9 ... 3.1
8.2---------0.8 .. 1.0 .. 1.0 .. 1.2 .. 1.4 .. 1.7 .. 1.8 ... 2.0 ... 2.2 ... 2.4
8.3---------0.6 .. 0.7 .. 0.7 .. 0.7 .. 1.0 .. 1.2 .. 1.3 ... 1.5 ... 1.6 ... 1.8
8.4---------0.4 .. 0.5 .. 0.5 .. O.6 .. 0.7 .. 0.9 .. 1.0 ... 1.1 ... 1.2 ... 1.3
8.5---------0.3 .. O.4 .. 0.4 .. 0.5 .. 0.5 .. 0.6 .. 0.7 ... 0.8 ... 0.9 ... 0.9
8.6---------0.2 .. 0.3 .. 0.3 .. 0.3 .. 0.4 .. 0.4 .. 0.5 ... 0.6 ... 0.6 ... 0.7
__________________________________________________ ____________

Once the total alkalinity and pH are known, the ratio between the partial pressure of CO2 due to the atmosphere on seawater and the actual pC02 of the system being evaluated can be determined utilizing the above chart. With the value from the chart known, you can decide whether you need to start ventilating the tank with outside air to your skimmer (or fans to the surface or remove glass tops) to degas the CO2 content or if you need to increase your alkalinity.

For example, if your alk in the tank is 10 dKH (9.8 is close on the chart) and you measure a pH in the water of 8.3, then you will read a value of “1.0” on the chart, telling you that your CO2 ratio is 1:1 with NSW during a normal day in the ocean. If you were to read a pH value of 7.9, you would know that your CO2 concentration is about 3 times what it would be in a daytime ocean reading, so it would be time to provide better gas exchange in your tank. If it were 7.7, then your tank would have 5.3 times the CO2 of NSW: in that tank, you would be having problems, either a tight lid or glass lids or a misbehaving CO2 solenoid or controller for a calcium reactor.

I really see no problem with your tank, it is WNL for most home aquaria.


HTH










*this includese coralline, any micro or macroalgae including those in the benthic biocoenosis, and your corals

[cronamator]

and there you have it. tom is the resident scientist. and not merely says so. but backs it up.

[tdwyatt]

Thanks, Frank!