System pH: Bare Bottom vs Substrate?

[AcroporAddict]

guys, I am on the learning curve with a new all SPS 465 gallon bare bottom tank. this is no tmy first SPS tank, but my first Bare Bottom SPS tank. Anyways, I had a 300 gallon all SPS system with a shallow substrate n dtransfered al lthe livestock to the new 465.

What I am wondering is if you BB guys ever noticed a drop in system pH vs using a system with a shallow substrate? My 465 system is now hovering at about 8.05 or so during the day and about 7.96 during the night, whereas formerly the system was at about 8.4 day and about 8.3 night.

I'm not trying to chase numbers, as my KH is at about 8.5 dKH, but I'm trying to understand why my system might be at a lower pH that before. All equipment is comparable. GEO 818CA reactor, alpha vetex 300 skimmer. Tank is located in the same room as before. All maintenance practices are the same. Tank is thriving, as a matter of fact. All pH probes are new and freshly calibrated.

Is there is some explainable reason for the difference in pH related to substrate vs no substrate, and is this even a factor?

Thanks or your help.
Dave

 

[dannyp02908]

are you using more CO2 on the reactor to supplement the larger tank? That could cause a lower PH. Also, i always thought that an aragonite based sand bed did help to buffer the PH at a higher level.

 

[ReachTheSky]

Aragonite sand slowly releases calcium carbonate which buffers pH. I don't know exactly how much but I'm sure it would depend on volume and surface area. It's likely that the absence of it is the cause of your pH being slightly lower if all other variables are the same.

 

[coralsnaked]

Is there is some explainable reason for the difference in pH related to substrate vs no substrate, and is this even a factor

Depends on the type of substrate previously used. If you were using a Carrabean style crushed coral, this was surely pushing your pH up to around 8.2. Aragonite substrate will have a simular affect on pH however not so pronounced.

Merry Skerry

 

[AcroporAddict]

are you using more CO2 on the reactor to supplement the larger tank? That could cause a lower PH. Also, i always thought that an aragonite based sand bed did help to buffer the PH at a higher level.

Aragonite sand slowly releases calcium carbonate which buffers pH. I don't know exactly how much but I'm sure it would depend on volume and surface area. It's likely that the absence of it is the cause of your pH being slightly lower if all other variables are the same.

Depends on the type of substrate previously used. If you were using a Carrabean style crushed coral, this was surely pushing your pH up to around 8.2. Aragonite substrate will have a simular affect on pH however not so pronounced.

Merry Skerry

Guys,
I appreciate al the responses, and thinking that the substrate buffers the pH of the water is what I would have thought until a few weeks ago, but I asked that same question here a few weeks ago, and was told by Bertoni that substrates are chemically inert at normal reef pH levels, and that the only thing that changes related to substrate vs removing it is the elimination in the activity of the nitrifying bacteria present on the substrate, and that there is no chemical buffering.

Assuming Jonathan is correct, then there is some other reason, and that idea about substrate buffering pH/KH is a myth.

Thread here: http://www.reefcentral.com/forums/showthread.php?t=2202127

You know, I was thinking about my BB system vs my SS system, and I have more fish and I feed more as well, so I wonder if that could be the reason for the decreased system pH? Biological activity (poop, etc) drives any system towards acidification, I think. So more bio activity could decrease the overall system pH maybe? I have 20 liters Seachem Matrix in the sump now, which is another change I did not previously mention. More Matrix than I need, but my sump is a 155 gallon MRC Bio-Sump, and that much was needed to assure all the water passes through the media. I will also say that after two months and moderate daily feedings, my nitrate continues to be zero, which is something Matrix claims to do in the inner, anaerobic areas of the media. Seems to be living up to its claims of denitrification.

 

[coralsnaked]

As aquarist we love to saturate our water with calcium carbonate minerals for the skeletal growth of our corals. The product generally coming from the Caribbean is mostly aragonite, making it suitable for reef aquaria, and it begins to dissolve at a pH of 8.2. This gives the CC the advantage that if your PH and Calcium levels drop lower than they should be the CC has the ability to leach calcium out into the water giving you a small boost. And when carbon dioxide (CO2) increases in our aquariums, a common occurance, we know our pH will fall and acidification rises. Further, if our aquariums pH falls by only .1 pH, this represents a 30%change in acidity using the standard Richter scale. This surely leads to slower coral growth and can actually erode corals. Taking into account this solubility of CC at a PH of 8.2 which is well within the normal reef pH parameters, how can we say that this substrate is chemically inert at normal reef pH levels, and that the only thing that changes related to substrate vs removing it is the elimination in the activity of the nitrifying bacteria present on the substrate, and that there is no chemical buffering. I won't go so far as to say there is even a substantial buffering but neither would I go on to say it is totally inert.

I would think after reading your 2nd post that surely there was more change going on to affect your pH than the removal of your substrate.

Merry Skerry

 

[dan-in-gr]

Hi, I took my 120 SPS only tank with its sand bottom out 2 months ago, and had zero change in pH. Love the bare bottom, Coraline is starting to grow on bottom and my tank is much cleaner, and now I can also put the narrow nozzles back on my Tunze's for more wave/flow action. Try raising your Alk.

 

[AcroporAddict]

As aquarist we love to saturate our water with calcium carbonate minerals for the skeletal growth of our corals. The product generally coming from the Caribbean is mostly aragonite, making it suitable for reef aquaria, and it begins to dissolve at a pH of 8.2. This gives the CC the advantage that if your PH and Calcium levels drop lower than they should be the CC has the ability to leach calcium out into the water giving you a small boost. And when carbon dioxide (CO2) increases in our aquariums, a common occurance, we know our pH will fall and acidification rises. Further, if our aquariums pH falls by only .1 pH, this represents a 30%change in acidity using the standard Richter scale. This surely leads to slower coral growth and can actually erode corals. Taking into account this solubility of CC at a PH of 8.2 which is well within the normal reef pH parameters, how can we say that this substrate is chemically inert at normal reef pH levels, and that the only thing that changes related to substrate vs removing it is the elimination in the activity of the nitrifying bacteria present on the substrate, and that there is no chemical buffering. I won't go so far as to say there is even a substantial buffering but neither would I go on to say it is totally inert.

I would think after reading your 2nd post that surely there was more change going on to affect your pH than the removal of your substrate.

Merry Skerry

Again, thank you for your response, but where does your information that aragonite dissolves at pH 8.2? This article by Randy Holmes Farley states it dissolves at 7.7 or below:

"Consequently, aragonite first becomes soluble in seawater when the pH drops below about 7.7 (this value might be more like 7.5-7.7 in reef tanks where the alkalinity is often higher than in seawater)."

Article: http://www.advancedaquarist.com/2002/3/chemistry

So if Randy is correct, then even at my pH of 7.96-8.0, the presence of Aragonite is not going to to be a factor r/t buffering, as you state.

 

[AcroporAddict]

Hi, I took my 120 SPS only tank with its sand bottom out 2 months ago, and had zero change in pH. Love the bare bottom, Coraline is starting to grow on bottom and my tank is much cleaner, and now I can also put the narrow nozzles back on my Tunze's for more wave/flow action. Try raising your Alk.

Thank you for your response as well. My alkalinity is currently 8.5 dKH. I really don't want to take it higher than that. I have just setup an MRC Nilsen Stirrer, so I will be topping off with Kalk. I figure that might help raise the pH some.

 

[bertoni]

Aragonite won't dissolve until the pH is very low, as inside a calcium reactor. Aragonite sand won't buffer the pH.

If a tank has a lower pH with a sandbed, which seems unlikely, I'd suspect the cause is insufficient aeration. The sandbed could be housing enough microbes to consume a fair amount of oxygen, although I'm still a bit skeptical.

 

[kaskiles]

Could you have adjusted your calcium reactor for the larger system, and possibly be depressing it with more CO2 injection?

It seems like the pH difference in this situation has to be CO2 (open windows in fall/winter Sourtheast) related. Larger tank placed in different room with different atmospheric conditions?

 

[downbeach]

I would suggest that since you increased your water volume by 50%(300 gal. to 465 gal.), and are still using the same skimmer, would be the most likely reason for this.

 

[AcroporAddict]

Could you have adjusted your calcium reactor for the larger system, and possibly be depressing it with more CO2 injection?

It seems like the pH difference in this situation has to be CO2 (open windows in fall/winter Sourtheast) related. Larger tank placed in different room with different atmospheric conditions?

Could be...but the equipment is not located in an unfinished part of the basement, not included in the air circulation of the house, where the CO2 should be higher.

 

[AcroporAddict]

I would suggest that since you increased your water volume by 50%(300 gal. to 465 gal.), and are still using the same skimmer, would be the most likely reason for this.

Was using a Royal-Exclusiv 250 Cone (Alpha Vertex), but am now using a RE 300 Cone (larger skimmer).

I have seen a slight increase in the pH since bringing the Nilsen Stirrer online. It peaked at 8.05 yesterday.

 

[swcc]

Could be...but the equipment is not located in an unfinished part of the basement, not included in the air circulation of the house, where the CO2 should be higher.

The surface area is lessened for aeration... in two ways: the water volume in tank to surface area of the tank, and also the volume of water to air draw of the skimmer. Thus the water has less opportunity to off gas co2 and equalize with the air surrounding it. I think downbeach is right.
Someone years ago did a mathematical example of air draw from a skimmer vs simply tank surface area.. the air provided 120x the surface area over the display for that example(he used x size tank and an average sized skimmer/air draw for it). Add 50% water volume and keep the same air draw and you get significantly less air to water interface for co2 equalization that cannot be made up by increased surface area of the tank.

 

[AcroporAddict]

The surface area is lessened for aeration... in two ways: the water volume in tank to surface area of the tank, and also the volume of water to air draw of the skimmer. Thus the water has less opportunity to off gas co2 and equalize with the air surrounding it. I think downbeach is right.
Someone years ago did a mathematical example of air draw from a skimmer vs simply tank surface area.. the air provided 120x the surface area over the display for that example(he used x size tank and an average sized skimmer/air draw for it). Add 50% water volume and keep the same air draw and you get significantly less air to water interface for co2 equalization that cannot be made up by increased surface area of the tank.

The skimmer I use now has two Red Dragon 1500s, vs one Red dragon 1500 in the previous one, and each has it's own air tube. So the skimmer itself draws 2x as much air as the old one, if that makes a difference.

 

[swcc]

yeah the way you answered dowbeach I assumed you were using same skimmer. twicethe air so twicethe surface area for o2 exchange so that is then not the situation. Now I am thinking you just have enhanced biological activity(more fishusing moreoxygen and more bacteria more co2) or the co2 in the surrounding air has risen. either way your certainly not in any problem ph wise so no worries.

 

[swcc]

should mention I typed my response to post 13. guess you added skimmer clarity same time as posted my response.

 

[kaskiles]

are you using more CO2 on the reactor to supplement the larger tank? That could cause a lower PH.

Maybe try the indoor version of the CO2 test, to help rule out the calcium reactor settings.

Pull a glass of tank water, set in the same room with a small air stone bubbling for 2 or 3 hours; pull the probe from tank and put in the glass.

 

[tmz]

All pH probes are new and freshly calibrated.



I'd bet on the new freshly calibrated probes unless they were used before the change . They tend to drift high overtime,ime.

Arognite is calcium carbonate, crushed coral is calcium carbonate. There is no difference between carribsea and other products of which
I am aware. I have no idea where that idea is from. It won't dissolve at normal reef ph levels. Some very small amounts might in localized low ph areas. Don't have any idea where that idea came from.