The use of CO2 injection in the reef aquarium--A discussion

[Nikkiheartsfish]

What's your opinions, guys? Discuss! This is a topic that interests me

I've noticed lately the trend in CO2 injection for reef aquariums. I've seen it for a while in planted tanks, but exactly how useful is such injection in a reef tank? It is my understanding, through some research, that CO2 lowers PH of the water and can cause corals and the calcerous skeletons of corals to disintegrate due to increased water acidity. Here are a few small snippets from some sites on CO2:

1. Influence of carbon dioxide on alkalinity
Carbon dioxide can change the pH of water. This is how it works:
Carbon dioxide dissolves slightly in water to form a weak acid called carbonic acid, H2CO3, according to the following reaction:
CO2 + H2O --> H2CO3
After that, carbonic acid reacts slightly and reversibly in water to form a hydronium cation, H3O+, and the bicarbonate ion, HCO3-, according to the following reaction:
H2CO3 + H2O --> HCO3- + H3O+
This chemical behaviour explains why water, which normally has a neutral pH of 7 has an acidic pH of approximately 5.5 when it has been exposed to air (http://www.lenntech.com/hazardous-substances/carbon-dioxide.htm).

2. "As atmospheric carbon dioxide levels continue to rise, so do the levels of dissolved carbon dioxide in sea water. This leads to an increase in ocean-borne carbonic acid, which is capable of dissolving calcium carbonate. 'This is a major problem for corals,' says Maoz Fine, a marine zoologist at Bar-Ilan University in Israel. 'Essentially, acidification leads to naked coral.' " (http://www.bioedonline.org/news/news.cfm?art=3235)

We know that the zooxanthellae within the corals photosynthesize to provide nutrients to the coral, therefore CO2 is of use to the reef aquarium, but...and here is where we discuss...


1. What would one have to do to keep the PH stable in such a tank that is being constantly injected with microbubbles of CO2? Would it be worth it? The cost of a calcium reactor (to maintain alkalinity and resistance to PH change) + a CO2 reactor is probably fairly expensive. (God forbid the bubblecounter breaks or your kid turns up the CO2 pressure, I've seen entire tanks of fish die that way).

2. That being said, would it even be worth it to have a CO2 injection system? Why not just a calcium reactor+adequate lighting+adequate surface irritation to maintain gas exchange?


Alright, I want to hear everyone's opinions who have an opinion on this matter. I will be imputting my opinion sporadically, as I already have put in a few of my own 2 cents, but I am mainly playing devil's advocate. Hope this turns out fun!

 

[Devilishturtles]

In my opinion you summed it up well with question #2. I can't see doing so because of the battle to maintain pH and alk. There are tanks which run completely smooth, very good coral growth, etc. with hardly as much as some powerheads for water flow on it and maybe a skimmer, and they are some of the most beautiful tanks I've ever seen.

I don't even see the need for a Ca reactor in most tanks unless they are VERY heavy in sps corals.

Meh, I don't see the point I guess.

 

[Nikkiheartsfish]

Thanks for your interesting input- I hope this topic gets more hits! The only thing I like about the calcium reactor is that it produces very bio-available calcium and that it takes care of itself practically. No fiddling around with kalkwasser Even if I had just some LPS I'd have one, just because I trust the type and quality of calcium coming from such a reactor. But that's another story. Anyone else? More opinions on the CO2 injection fad that has developed as of late?

 

[MT79]

I agree w/ DT. For a tank w/ LPS and maybe a couple SPS dosing a balanced two part Ca/Alk or using kalk will be much easier. It would take awhile for cost to even out as well, so that should be cheaper. Ca reactors, from what I have read/heard from other reefers, require regular "tinkering" with, and constant tank PH monitoring. Unless the tank is SPS dominated so there is atleast a useage of ~ 10ppm Ca and ~.75 meg/l Alk daily, I think a two part and/or kalkwasser stirrer may be a better option. Many people choose to run a kalk stirrer in conjunction w/ a Ca reactor to avoid the low PH Ca reactor generally cause.

 

[Lepomis]

I look forward to seeing the responses since I am a new to the salt scene. Interesting how trends go, what was hot fades and what works comes back at some point. I think it is like many things in that it won't make or break a tank but the proper use can only help. Funny that you mention recent trends that CO2 is being used. I am just getting started in a saltwater tank and have several books that came with a tank I bought from a lady. All the books are from the late 80's and all contain chapters about using CO2 in the "modern' day reef tank. Much of the books seem to focus on salt water reef tanks and how the Europeans (Germans mentioned often) run them. From the overall tone of the books it seems that Americans were slow to adapt to many techniques. Carbon dioxide was typically stressed for helping maintain a healthy balance of macro and symbiotic algaes. Control of carbonate hardness (high) is suggested in these books to maintain higher levels of CO2. Most stress that the CO2 will be used by the macro and symbiotic algae instead of them turning to carbonates and bicarbonates thus decreasing the buffering capacity of the reef system. They go on about how to test if I recall and hit some other potential benefits and how it effects the system. I believe they mentioned for a visual indication of enought CO2 that if one keeps Caulerpa species you should see oxygen being released or pearling as described so often in the freshwater planted realm. Some of the information is outdated but most is based upon scientific works and "experts" in the field and to me very sound information to follow. The books were written by Albert J. Thiel, Advaced Reef Keeping and The Marine Fish and Invert Reef Aquarium. Protien skimmers, ozone, redox potential, cycling methods, etc... is covered

 

[MT79]

That being said, would it even be worth it to have a CO2 injection system? Why not just a calcium reactor+adequate lighting+adequate surface irritation to maintain gas exchange?

Funny that you mention recent trends that CO2 is being used. I am just getting started in a saltwater tank and have several books that came with a tank I bought from a lady. All the books are from the late 80's and all contain chapters about using CO2 in the "modern' day reef tank.

I thought Ca reactors always used CO2 in order to get the PH in the chamber low enough to dissolve the media making the Ca/Alk available. Am I wrong?? Is CO2 injection different and used on it's own w/ out a reactor?

 

[Lepomis]

Like I said I am a newbie and some of the info is likely outdated or has been improved. So much information out there to wade through. They talk about CO2 usage it seems as two aspects. In what I assume in a Ca reactor (they use coral fragments). However they seem to indicate that besides as you described dissolve the media to increase Ca/Alk availibilty it also serves to increase actual CO2. At higher dKH higher CO2 levels can be obtained . One of the effects of increased dKH is that that the water can contain higher levels of CO2. I believe some of the symptoms of low CO2 they mentioned as the decline and slow growth of macro algaes, symbiotic algaes within inverts not being able to perform and invert die off over time. If neither are kept then CO2 is not an issue according to the books. They mention in the Advacned Reef Keeping, as I understand it, to be a stand alone CO2 reactor and wanting levels around 3 to 4 mg/L.

 

[MT79]

Gotcha. Funny, most people spend so much time trying to decrease CO2 in the hopes of improving PH levels. It's not something I normally think of as limited or even very important. But it is, obviously. Low levels of CO2 are generally not something that seems to be an issue though, at least from what I've heard/read, but I have never looked for info on that particular subject. As I said, people battle w/ "high" levels in order to raise PH.

Now I have to wonder w/ all the flow, macro algae and corals in my tank, if my CO2 levels are optimal. Thanks, one more thing to contemplate LOL j/k

 

[Phyl]

I've never heard of CO2 being "dosed" into a tank for any purpose other than reducing PH for a Ca reactor. The two chamber Ca reactors do a fairly efficient job of elevating the PH in the second chamber after the initial calcium breakdown in the first chamber.

We do keep a fan blowing across the sump to help blow off the excess CO2 and help to elevate the PH. I can't imagine ADDING CO2 to my system over and above what I have now!

 

[DavidStang]

Raising macro algae

I've got 7 interconnected tanks devoted to raising macro algae. They are dedicated to this purpose, and don't contain corals, fish, or invertebrates. My mission is to get this algae to grow as fast as possible.

The tanks are on an experimental light cycle of 6 hours on, 2 hours off, repeated 3 times each day. Tanks are enriched with the skimmate from my protein skimmer for my reef system.

I happen to have a good calcium reactor available. I could convert the reactor to a CO2 injector by using the CO2 tank and regulator, and removing the media from the injector's big tank. Or I could just run the calcium reactor as it was intended, even though there will be no critters requiring calcium.

Because CO2 injection produces such fabulous results in freshwater tanks (and is entirely safe if there are no fish), it seems like CO2 injection should be a good idea in my macro algae project.

My questions: should I run the reactor with or without the media? Does anyone know the pH tolerances for things like grape leaf caulerpa?