CO2 scrubber

[tmz]

I bought the soda lime in a 5 gallon bucket but use much less than that at one time.

When you dose limewater, the calcium hydroxide you add disssociates to Ca
(calcium) and OH- hydroxide. The hydroxide joins up with CO2 very quickly , raising the ph at that point in time not later on.

The ph point a which biotic calcium carbonate precipitation would cease or reverse, where coral skeltons or oyster shells,etc. would dissolve,is generally cited at around 7.7 but it depends to a degree on alkalinity levels too. Low ph , low alkalinity and low calcium each make it more difficult for organisms to calciify. So it would be difficult to run a system where all were pushing the low side of their ranges.Conversley, lower ph ranges may be more tolerable where there is an abundance of carbonate alkalinity and calcium.

[Gravesj1s]

Originally Posted by tmz

So, on the one hand higher ph(less H+ in the water) makes it easier for them to squeeze out a positively charged proton when there are less positively charged H+ protons in the water. thus it would seem higher ph might make precipitation and skeletal growth easier. However ,recent discussions suggest higher proportions of HCO3 vs CO3 which occur at lower ph ranges may be more beneficial overall. A shortage of HCO3 vis a vis CO3 might actually slow growth even though more CO3 results in higher ph and alkalinity( CO3, carbonate can neutaralize 2 H protons before becoming carbonic acid H2CO3 while bicarbonate, HCO3 has room for just 1).

Mind if I ask you flat out where I can find these discussions you are refering to?Don't mean to be so blunt but I just read a 15pg thread didn't really see much.-Graves

Many systems running low or ultra low nutrients shoot for 7 or 8 dkh to avoid burnt tips where calcium carbonate skeletal growth seems to outpace tissue growth. These lower alk values often mean less buffering capacity and lower ph as well. Reef surface waters run around 8.2ph. The range of 7.8 to 8.5 should be sufficient for growth. Below 7.8 and you risk coral skeleton dissolving. Higher than 8.5 and abiotic(non biological) precipitation of calcium carbonate is likely ,including "snowstorms" which not only deposit calcium carbonate crystals every where but also drop calcium and akalinity precipitously These alkalinity bounces can be deadly to sps in particular ,in my experience.

With low nutrients you are refering to inorganic N and P , I've seen you mention this before in this forum.If skeletal growth is out pacing tissue growth how is it ruled out that nutritional needs are actually being met?-Graves

[Gravesj1s]

Ok, I think I found it.Zeovit threads in the chemistry forum.I was looking in the sps forum.

[tmz]

Originally Posted by Gravesj1s

With low nutrients you are refering to inorganic N and P , I've seen you mention this before in this forum.If skeletal growth is out pacing tissue growth how is it ruled out that nutritional needs are actually being met?-Graves

I don't think it does. It seems at ultra low levels of nitrogen as measured in inorganic NO3 that corals are more sensitive to alk swings.Higher alkalinity levels seem to bring on burnt tips by a number of anecdotal accounts. Thus ammino dosing is thought to help provide more nitrogen. No one really knows what causes burnt tips, I know at very low inorganic nutrient levels, if alk climbs much past 10dkh in my system burnt tips will follow. Wether bacteria are reacting to the extra carbonate alkalinity in some pathogenic fashion or increased skeletal growth without equal tissue growth or something else causes it, I don't know.

[tmz]

Originally Posted by tmz View Post

So, on the one hand higher ph(less H+ in the water) makes it easier for them to squeeze out a positively charged proton when there are less positively charged H+ protons in the water. thus it would seem higher ph might make precipitation and skeletal growth easier. However ,recent discussions suggest higher proportions of HCO3 vs CO3 which occur at lower ph ranges may be more beneficial overall. A shortage of HCO3 vis a vis CO3 might actually slow growth even though more CO3 results in higher ph and alkalinity( CO3, carbonate can neutaralize 2 H protons before becoming carbonic acid H2CO3 while bicarbonate, HCO3 has room for just 1).

Mind if I ask you flat out where I can find these discussions you are refering to?Don't mean to be so blunt but I just read a 15pg thread didn't really see much.-Graves

I found it.One search of the chemistry forum on carbonate bicarbonate ratios. I'm sure there is more.
Here it is:

http://www.reefcentral.com/forums/sh...rbonate+ratios

[Gravesj1s]

Thanks,

I have been keeping a pretty good log on Ca,alk, ph using just limewater and I think I got a good handle on it now.Huge difference between the kalkreactor and still resevior 24/7 dosing.Really want to post up all the numbers and run it by you and anyone else.I haven't done the sump in a closed bucket yet but I think that is the part where I might start looking at the co2 scrubber.

[pascal32]

great stuff! I love the idea, slightly concerned as to the repetitive costs. Looking at the $90/5 gallons compared to on-line prices does help. thereefguys are coming in at $54/gallon - that puts you at almost %70 lower!

please keep us posted! I'll probably jump on board as soon as there is more data on lifespan of the media.

[tmz]

Gravesj1s. You are welcome. Be happy to look at your data when you are ready.

Blurry, Still going on about a liter and a half for 550 gallons. All I see so far are a few purpling patches. I'll keep tracking it for a few more weeks.

[Gravesj1s]

Tmz~ I hope this is alright to post here,I thought it was interesting and that you other members here might want to have a look ,if you haven't already.

Effects of variations in carbonate chemistry on the calcification rates of Madracis auretenra (= Madracis mirabilis sensu Wells, 1973): bicarbonate concentrations best predict calcification rates

From the Abstract:
Physiological data and models of coral calcification indicate that corals utilize a combination of seawater bicarbonate and (mainly) respiratory CO2 for calcification, not seawater carbonate. However, a number of investigators are attributing observed negative effects of experimental seawater acidification by CO2 or hydrochloric acid additions to a reduction in seawater carbonate ion concentration and thus aragonite saturation state. Thus, there is a discrepancy between the physiological and geochemical views of coral biomineralization. Furthermore, not all calcifying organisms respond negatively to decreased pH or saturation state. Together, these discrepancies suggest that other physiological mechanisms, such as a direct effect of reduced pH on calcium or bicarbonate ion transport and/or variable ability to regulate internal pH, are responsible for the variability in reported experimental effects of acidification on calcification. To distinguish the effects of pH, carbonate concentration and bicarbonate concentration on coral calcification, incubations were performed with the coral Madracis auretenra (= Madracis mirabilis sensu Wells, 1973) in modified seawater chemistries. Carbonate parameters were manipulated to isolate the effects of each parameter more effectively than in previous studies, with a total of six different chemistries. Among treatment differences were highly significant. The corals responded strongly to variation in bicarbonate concentration, but not consistently to carbonate concentration, aragonite saturation state or pH. Corals calcified at normal or elevated rates under low pH (7.6–7.8) when the seawater bicarbonate concentrations were above 1800 μm. Conversely, corals incubated at normal pH had low calcification rates if the bicarbonate concentration was lowered. These results demonstrate that coral responses to ocean acidification are more diverse than currently thought, and question the reliability of using carbonate concentration or aragonite saturation state as the sole predictor of the effects of ocean acidification on coral calcification

[Gravesj1s]

I cant help ask here as I think I'm missing something though after reading that..From what Im getting a higher Ph would shift the ratio to more carbonate less bicarbonate side.

So ,I cant help ask here why the scrubber would be of benefit? Honestly ,I thought alot about this but stumped here....

[tmz]

Yeah, it's a bit arcane ,particularly since there is debate over what the optimal ratio between HCO3 and CO3 is in variable tank conditions.
The scrubber just let's you move ph up without directly affecting total alkalinity since you are not adding any CO3; your not adding any H either as you would with bicarbonate(HCO3) additions.
Normal seawater at 8.2 has a ratio of around 110 bicarbonate to 20 carbonate if I recall correctly .(Note: 1 meq/l alkalinity is about 50ppm, 2.8 dkh) If you had 130 ppm in your tank the 130ppm wouldn't change unless you added carbonate or bicarbonate.

Yes, the ratio between carbonate and bicarbonate will change in response to ph. Higher ph = less H = more carbonate and less bicarbonate. A higher ratio of carbonate will increase buffering capacity ,which is not the same thing as alkalinity. Carbonate adsorbs 2 H+ protons before becoming carboninc acid while bicarbonate (HCO3) adsorbs only 1.Ph as you know is a measure of the water's ability to neutralize acid.

Our tanks aren't oceans and our homes aren't global air masses .Excess CO2 can easily build up and depress ph via H additions from hydrolized CO2 forming carbonic acid even when alkalinity is high. CO2 can get high in a tank if the air around the tank is high in CO2 as well as from CO2 contributions from the concentrated bio activity in the little droplets we call reef tanks. While the tank will equilibrate with the air eventualy, it takes a bit of time; it's faster with more surface agitation or bubbling like a skimmer. A way to limit CO2 input at least from the air pumped in from the skimmer is a useful way to lower the CO2 level in the tank.

What is optimal ph for a particular aquarium is really the heart of your question,I think?

The scrubber just gives you an ability to raise phin an efficient way without adding alkalinity when you think you should raise it.

Recommended range for ph are 7.8 to 8.5. I'm trying to aim for 8.2( when in doubt I follow mother nature ). 8.2 or 8.3 is also mid point in the range, so risks of dissolving coral skeletons or precipitating calcium carbonate are lessened. However, what the best ph is for various specimens and and systems varying in nutreints and other variables is highly debatable.
The scrubber is just a tool which enables some direct ph control without adding anything to the tank but air with little or no CO2 in it..

[Gravesj1s]

Yeah I pretty much got the gist of how the scrubber works and the reason your using it.I posted that abstract up partly to see if anyone else would chime in,didn't work well so, I had to ask,LOL.

Initialy when this thread began I assumed from everything I've ever read in the past the ideal Ph where calcification was maximized was near 8.4.now the lower numbers you posted of your tank seemed to make sense on why you were going with the scrubber.

Reading from that abstract though casts a whole new light on things.To be specific, the low Ph range (7.6-7.8) where calcification was normal and even elevated ,directly relating to bicarbonate.Shocking ,too.

Also, I understand why your shooting for the 8.2 -ish range being average for nsw and that makes sense.

[tmz]

That paper was cited by the same fellow who contributed the high alk equals more growth stuff a few years ago. I think there will be more research on ph tolerance/ coral adaptation in reaction to concerns about acidification of seawater from higher athmospheric CO2 .

Scrubber still working. Get a 1.8 point bump ,now using a scrubber on each of the two skimmers. The first liter went into service on 8/9 and still appears far from exhausted, just some purpling in the bottom inch or two

[pascal32]

Tom - how is the media holding up?

While battling the dinos I put on a co2 scrubber to bump ph- I went from 8ish to a solid 8.2 going full out (tamped up the flow with a t). I'm passing through a media container in a canister just like a di unit. Media consumed in about 3 weeks, ph dropped right back down.

Thinking of heading to airgas!

[Gravesj1s]

I'm just more curious at the moment with the overall thread and the experiences in general. Currently I see no need for me to use a scrubber.

-Blurry,how much media did you use in the 3 weeks ,I remember seeing it hooked up but didn't notice how much was in the canister?

[pascal32]

Tom - is this the right stuff?

http://www.airgas.com/browse/product...t=MOP120020-00

[pascal32]

Originally Posted by Gravesj1s

I'm just more curious at the moment with the overall thread and the experiences in general. Currently I see no need for me to use a scrubber.

-Blurry,how much media did you use in the 3 weeks ,I remember seeing it hooked up but didn't notice how much was in the canister?

I got mine from the filter guys since I was ordering DI and was short on time to run to airgas and make my own reactor which is what I should have done.

The site says 1 gallon does 6 cartridges, so about 1/6th of a gallon which is a little over 2 1/2 cups.

I'm feeling this - I swear the Dinos came to a screeching halt when this went on line. Since its faded it seems that they are starting a comeback.

BTW - thanks for the lighting suggestion - the tank has took off since I changed the light schedule, growth is ridiculous & color is coming back strong. groeth has gone up so much I'm dosing almost twice what I was before - up to a 150ml/day rec 1 two part. the caps are growing like crazy and coraline is setting in everywhere!

[tmz]

Yes, the sofno lime is the right stuff . I'm getting a steady .2 increase as well. I changed a liter of media after 5 weeks . It was still 40% white. I've left the other one going for 5 weeks now. So I would say for a skimmer drawing 1500gph of water ,one liter of sofno lime in my house air will last about about 6 weeks perhaps as much as 2 months.. At $4.50 per liter it's not very expensive.

[pascal32]

Cool. I called airgas and the sofnolime will be here early next week

Thanks!

[mr.maroonsalty]

I'm seeing it in medical supply catalogs for ~$2.50 # Do you have an idea what the volume of a # of this material is?

[pascal32]

Originally Posted by mr.maroonsalty

I'm seeing it in medical supply catalogs for ~$2.50 # Do you have an idea what the volume of a # of this material is?

the 5 gallon bucket lists a net weight of 37 pounds.

5 gallons/37 lbs = .135 gallons/pound
.135 gallons/pound * 16 cups per gallon = 2.16 cups/pound

prince wise @ 2.50/pound:

$2.50/# * 37# = $92.50 for 37#

cost is higher than buying the 5 gallon pail through airgas.

[tmz]

I paid $81 plus tax for the 37 lb /5 gallon bucket from Airgas, ie $2.19 per lb plus tax. It might be worth it for some to buy it in smaller sizes. I could not find a vendor with a reasonable price for smaller amounts. On line hobby vendors go about $40 to $50 per gallon.
Robert,do you know of vendors who sell in smaller quantities @$2.50?

[mr.maroonsalty]

I see it here: http://www.shopmedvet.com/product/so...hesia-products I haven't searched much. My other is a vet; she said they keep it by the bucket.

[tmz]

Nice , Thanks for the link. I bet many folks would prefer the 3lb size even if it's a little more expensive rather than going for 37 lbs at once.

[NyReefNoob]

couldn't you also just use a air pump with a air stone ?