Calcium Reactor

[Gordoe]

Anyone running CA Reactors who have had ill effects, ie Hair Algae blooms. I heard that the CO2 can cause outbreaks or make a small problem worse, much worse.

Trying to move past hearsay and onwards to actual experience..

I have the plans and the material for my DIY CA Reactor and getting ready to start, just wondering if I should wait until the hair algae is all gone..

Tia
Gordoe

[reefburnaby]

Hi,

Impurities in the calcium carbonate can be dissolved by the reactor and release the silicates or phosphates in to the water -- making the algae grow better :) Higher quality calcium carbonate (like ARM) should prevent this from happening.

In any event, hair algae may receed when you use the reactor because the alkalinity will rise and hair algae don't like that as much.

As for excess CO2, I use dual stage calcium reactor. The second stage slowly reacts with any residual CO2 in the effluent. Since the effluent is flowing very slowly (100ml per minute or so), it will have lots of time to react within the reactor.

Hope that helps.

- Victor.

[Jamie Cross]

Victor,
You running your reactor at 100ml/min? if so how bigs the tank and whats in it and also whats your effleunt ph?

[reefburnaby]

Hi,

Yupe...100ml/min or about 1 to 2 gallons an hour. My tank is a 90 G. It is filled with softies and LPS. Put it this way...these same corals were in a 20 gal (very overpack 20gal) AND kalk+vinegar could not keep up with the calcium. I was dosing buffer every 2 days at the maximum strength and dosing "extra" calcium every week. Still..my levels were very wonky. After 8 months of dosing at these levels, I had enough of my 20 gal and move it on to a calcium reactor + a 90G.

Effluent PH - 7.6 to 7.8. I know what you are thinking (and thanks for being concerned :) )...typically people use 80dpm (say one drop is 1/10th of a ml, that's about 8ml/min). But we are talking about a dual chamber reactor, so you can run the effluent a bit faster.

If you have ever used a Tap Water Purifier, usually 1 to 2 gallons an hour is a good rate for the purifier -- although it is rated for 10 gph. My reactor is about same volume as the TWP...so, it should have plenty of time to react with the remaining CO2 at 1 to 2 gallons per hour. :)

Why do I run it so fast...prevents my reactor from clogging up. Also, it helps balance the reaction load between the two chambers and it places less stress on the circulation pump.

Hope that helps and sorry for the confusion.

- Victor.

[Jamie Cross]

Victor,
No confusion, I was expecting the high ph out of the effleunt.
Also if you don't mind could you tell me your effleunt alk in meq/l and tank alk.
Thanks Jamie

[Jamie Cross]

Victor,
As for your typical effleunt statement I would have to say that is false as there is no such thing as typical as every systems demands are different there for your numbers as far as effeunt rates and co2 b/min will also be different. The way you are running your reactor would infact add little to your tank as far as alk and calcium are concurned. I would geuss and say that your effuent perameters are not all that much more then tank paremeter as with such a high ph you would be desolveing very little media.
Jamie

[Lock]

I would have to agree with Jamie. At the PH you are running your calcium out put would be almost nothing. To get any productivity from the reactor the effluent needs to be below 7.0 or in the acidic area. I would say that you are just getting out what you pump in. My DIY reactor is most productive when the effluent is running at 6.4 - 6.6. I maintain a calcium level of 450 using it. Here is a picture of my reactor.
http://home.att.net/~lockarts/4Reactor.JPG

LOCK

[reefburnaby]

Hi,

Just checked...Effluent has a dkH of 15-20. pH is 7.6-7.8 and tank dkH is around 10-12.

Calcium reactors don't instantly dissolve calcium carbonate at a specific pH.

I guess we need to define some terms. pH is the measure of how acidic or how basic a substance is. A pH of 7.0 is consider to be netural (neither base or acid). What makes a substance acidic or basic is the proportion between H+ and OH- ions. The more H+ ions you have, the more acidic the liquid becomes (vice versa for OH- ions...except it makes it more basic). For reference, pH is defined as :

pH = -log(H+)

More H+, lower number and its logarithmic. Hence, pH of 4 has ten times as much H+ as something with a pH of 5.

Now, when we inject CO2 in to the water (H2O), we are doing the following :

CO2(g) + H2O <-> 2H+ + CO3--

So, we get an two H+ ions and one CO3-- (carbonate ion). Since, we are adding more H+ with each CO2, we will be decreasing the pH. When we include Caco3 (calcium carbonate or calcium reactor media), we get this:

CO2(g) + 2H+ + CO3-- <-> 2(HCO3-) + CO3-- + Ca++

Notice that we get two bicarbonates (HCO3-), one carbonate (CO3--) and Ca++. The bicarbonates and carbonates are what form the alk and it controls the pH. Ca++ is the calcium ion.

What does this mean -> the more H+ we use, the more Ca++ we have in the water due to the reaction.If the effluent (water coming out of the reactor and in to the tank) has low pH, that means that you haven't used all of the H+ in the water that you injected via CO2. Hence, you are effectively wasting that CO2 and it must be blow off by the skimmer, water-air exchange or react with the bicarbonates or carbonates. The second stage in the calcium reactor reacts with the remaining H+ -- its not perfect though. Even with a pH of 7.6, I am still adding H+ back in to the tank (my tank has pH of about 8.2) which must eventually be removed.

Hope that helps you understand how a calcium reactor works and why higher pH effluent is possible and highly desireable. As you have notice, I tend not to follow any rule of thumbs. I take a more scientific approach and understand what is going on. For me, a depressed pH is not a good think for a tank....hence the higher pH for my effluent.

- Victor.

[Jamie Cross]

Victor,
what you are saying will work on a low demand tank such as yours but there is no way in the world that it would work on my system. Like I said earlier you are adding very little to your system threw your reactor and would also say wasting co2.
jamie

[Lock]

The easiest way to view the functioning of the reactor is as a reverse calcification process. The idea is to dissolve a calcareous media in such a manner that it provides both bicarbonates HCO3- (alkalinity) and calcium (Ca++) ions in the same ratio as they are consumed during calcification. Effective dissolution of the calcareous media requires that the solute be at an acidic pH. Because saltwater is usually at a pH of 8.0 and higher, we need some way of reducing the pH in the reactor to aid the dissolution of the media. Carbon dioxide (CO2) is used to help lower the pH in the reactor, and the general reaction form is as follows:
CaCO3 + H2O + CO2 <——> Ca2+ + 2HCO3-

So, the calcium carbonate reactor is basically a device that brings the three ingredients — water, CO2 and calcium carbonate — together in a manner so as to allow efficient production of HCO3- and Ca++ ions. All reactor designs basically follow the same principle, but differ in the techniques to create the circulation loop, the manner in which CO2 is injected, how the water is input to the reactor, and how the effluent is drawn off.

I find it much easier to adjust the reactor based on the alkalinity output rather than the pH measurement. I would recommend first setting up an effluent flow rate so it flows in a continuous steady drip, and then making adjustments to the CO2 flow rate to increase or decrease the alkalinity of the output. For most tanks this approach will work fine, but if you have a heavily loaded small-polyped scleractinian (SPS) coral tank, then it may require you to increase both the effluent flow rate and the CO2 injection rate. A certain amount of fine-tuning is required to adjust the reactor for your particular system.

Having a good estimate of the daily consumption of the alkalinity in the tank and understanding some of the “reactor math” can help in eliminating some of the trial and error in fine-tuning the reactor. Let us assume that the reef system contains T liters of water, and the effluent flow rate is L liters per hour and the estimated daily alkalinity consumption is c milliequivalents per liter (mEq/L) per day. Now, measure the alkalinity in the tank and the alkalinity of the effluent. The difference between the two values will give you the increase in alkalinity due to the reactor — call this d (mEq/L) — as follows:

alk/day added due to the reactor = (d x L x 24)/T Equation 1

So, now we need to adjust the reactor so that the daily increase due to the reactor is approximately c mEq/L. This will give us the setting at which the reactor will replenish the alkalinity that is consumed daily.

Looking at the Equation 1, we can see that there are three ways this can be achieved:
Only adjusting d — the increase in effluent alkalinity
Only adjusting L — effluent flow rate
Adjusting both d and L.

The effluent alkalinity can be increased (or decreased) by correspondingly increasing (or decreasing) the amount of CO2 and keeping the effluent flow rate constant. This provides one convenient way of tuning the reactor output to the aquarium needs. When increasing the amount of CO2 added care must be taken to keep the pH level above approximately 6.3. I personally use this approach to adjust my reactor. If I find that I have to injected too much CO2 so as to cause the pH in the reactor to drop below 6.3, I am better off also increasing the effluent flow rate through the reactor.

Increasing the flow rate will result in a decrease in effluent alkalinity if the CO2 flow rate is not simultaneously increased. Several manufacturers recommend adjusting both the flow rate and the amount of CO2 simultaneously to maintain a constant pH (about 6.5) in the reactor and hence a constant alkalinity output in the effluent. I prefer having to just adjust one parameter — the CO2 flow rate. Both approaches will satisfy the needs of the user, but the key is to balance the daily consumption to the daily addition of alkalinity.

[reefburnaby]

Hi,

Yupe..I agree. The reactor should be adjust to your system's demands.

Low demand system...ha ha ha...too funny. Wasting CO2...even funnier. At least I don't have to dose anymore and my corals are happier than ever because the tank parameters are more stable.

Oh well...tried to convince you guys but I guess I failed. Maybe I'll try again someday.

- Victor.

[Jamie Cross]

Victor,
You lost me there low demand system (funny) are you telling me something different? It's very clear if you can get away with those numbers your running your system at, it's sucking up very little calcium. wasting co2 even funnier lost again if you turned down your effleunt you could turn down co2 and get better effleunt alk and calcium there for waste less co2. You clearly have very little experience with a reactor and even less with a high demand system so to me thats even funnier

Hope that helps,
Jamie

[Troy F]

Hi guys. I took the liberty of asking for Randy's opinion on this one. Here is his take on it:

.....

I agree with Victor's chemistry and his assertion that the effluent pH can be high.

I agree with Jamie that Victor is adding little to his tank. Victor claims he has:

"Effluent has a dkH of 15-20. pH is 7.6-7.8 and tank dkH is around 10-12. "

All that is fine. I convert those to be about 6 meq/L and 4 meq/L respectively.

The kicker is the 1-2 gallons per day flow rate. In a 90 gallon tank, he is boosting the total tank alkalinity by 0.02 to 0.04 meq/L per day.

Compare that to limewater. Assume 1% evaporation replacement with limewater that is 40 meq/L. That process then adds 0.4 meq/L per day to the total tank alkalinity.

Consequently, Victor has his chemistry right, but the addition that he is getting is less than 10% of that typically gotten via limewater.

Anyway, that's my quick take.


__________________
Randy Holmes-Farley

Victor you have the science right but Jamie's experience should be very obvious when you look at his tank :) .

[reefburnaby]

Hi,

No argument with Jamie's tank...looks really good. And I am not questioning his abilities. So, Jamie, I hope that I didn't hurt your feelings with these discussions. But, I will try to explain what I found funny....

Low Demand Tank.

What in the world is a low demand tank ? Funny. Yes, because it references to some "standard demand tank". Is there one ? Probably not...since it is highly dependant on the animals that are kept. Can one assumes that LPS and softies have low demand ? ...that is not always case. Can one assume that SPS is a high demand ... again not always the case.

Wasting CO2.

Huh...I just spent 15 minutes explain that high pH effluent means that most of the CO2 is being used up...hence less CO2 wastage. And then, I hear comments that I am wasting CO2. Oh no...I have to re-explain it again ? An endless circle...that's what I find funny.

My Tank and My Experience

Oh man... I am trying okay. I have never assumed or stated that I am an expert in reefing. I try to give the best advice that I can offer to those who ask.

Just wanted to point out...the effluent rate is 1 to 2 gallons an hour...not day. So....that's 0.48 meq/l to 0.96 meq/l per day. Jamie...is that why you are confused ?

Hope that answers your questions and comments.

- Victor.

[Andy]

Hello

I think where the confusion is arising is that you guys don't realize that Victor is running a dual stage reactor. With most single stage reactors, the manufacturers recommend an effluent pH of 6.5. This pH allows for maximum dissolution of the aragonite reactor media. Agreed? What we are trying to get away from is adding effluent at such a low pH into our systems. This is accomplished by adding a second reaction chamber filled with aragonite. Low pH effluent exiting the first chamber then passes through the second chamber where some of the excess CO2 (which reacts with water to form carbonic acid) is used up. As the residual CO2 is exhausted, the pH naturally comes up (basic principle of buffering). Calcium, carbonate and bicarbonate ions remain in solution even at the higher pH. With my dual stage reactor, effluent leaving the second chamber would typically have a pH of 7.5. The pH of the solution circulating through the first chamber would be at 6.5. Some people with single chamber reactors will let their effluent drip into a container to allow for degassing of excess CO2 prior to overflowing into their sumps. This degassing causes the pH to rise while maintaining the calcium, bicarbonate and carbonate ion concentrations. So to summarize, I don't think the pH of the effluent leaving the second chamber is the critical parameter to measure, its the pH of the effluent circulating through the first chamber. If that can be maintained in the 6.5 to 7.0 range, you should be dissolving enough of the aragonite to support your systems. If your calcium and alkalinity are falling within your tank, you need to increase the effluent drip rate while maintaining the low pH in the circulating chamber. This is achieved by increasing the CO2 bubble rate. Its a fine balance that requires some patience but once your reactor is dialed in, additives are a thing of the past.

Hope this dialogue helps.

Andy

[Jamie Cross]

Guys I don't care about the science of all this stuff I don't have the education to make me understand it nor do I wish to. I enjoy reef keeping and I will leave the tecnical stuff to the experts. That is why I read many arcticles and books and also internet topics and make conclusions from those who are experts in the hobby and in a feild relevant to it. What I was tring to say was Victors idea about how to run a reactor will work on his low calcium demanding system(meaning your system uses up very little calcium compared to my system)but I would have to run a 200gph pump directly thought the reactor and go though 20 lb co2 bottles like they were candy if I were to run it in that same manner(not exactly but hope you get the idea) and I still don't think that would be enough to work anyway, I am not a technial reefer I am a layman reefer.You all do as you wish I was just making apoint that to me it was not practical to do what your doing but hay feel free. I also suppose this is another reason I read more then I post. It's just not worth the bs that goes with posting. Andy I also run a dual chamber reactor and at such a high effleunt would do very little in raising the ph unless the second chamber was huge. The only reason I run a second chamber is to allow extra contact time with the media it would make more sense just to build a bigger reactor but was very easy to make the second chamber so did that instead. oh well I geuss thats why it's better to keep ones opionions to themselves some times. I geuss I'll just keep reading Jamie

[Jamie Cross]

Victor,
I've decided to take some numbers for you and perhaps u could tell me how it would be possible to get the numbers I need to maintain my alk at about 4.5meq/l or 12.5dkh useing the theory you use.

second chamber effleunt ph 6.65
first chamber effleunt ph 6.53


second chamber effleunt rate 105 ml/min
second chamber effleunt alk 11.42meq/l or 32 dkh
Any other numbers that I have left out can be given
Jamie

[reefburnaby]

Hi Jamie,

Sorry for the delay (I have been rather sick for a while),

I am missing a number : what is your alk consumption ? And how much water is in your system (just water...no sand, rocks and an estimate is fine).

Another question...what does your second reactor look like. I seem to recall a vessel made from water filter.

- Victor.