How do calcium reactors automatically keep up with coral growth?

all of it besides water flowing through it

 

They keep up with a steady demand, not a changing or increasing demand. I would still take a reactor over dosing any day since the adjustments are miniimal as is the maintenance. I fill the CO2 bottle about every 9 months and add media every 6 months, thats about it. While my reactor is out of service I am dosing and its a royal PITA.

 

ha, yeah. i do crazy amounts of water changes now and am planing on setting up a 2part or reactor set up. not trying to turn this into a 2part vs reactor debate, but that is what i was getting at. i still think i am leaning towards a reactor, still seems like less work to me.

 

Well I have heard it stated too.... that reactors keep up with CHANGING demands. Never cared but never really understood how that was. Now if Reactors are just a source and have to be tested and what not like two part, then I really don't get how vastly superior they are. I mean in this hobby there are usually a couple of ways of doing things... yet reactor lovers talk about how superior they are to 2 pt. on this very issue alone... yet it isn't the case and this just comes down to a another "6 or half a dozen."

We all seem to have our routines and it's a HUGE difference between what one person thinks is "too much" work to what another person thinks. Two part is not anymore work that a reactor as long as we are comparing apples to apples and both are automated. My pumps came on all by them selves and I shook a couple of jugs for 10 minutes every 4-6 weeks. Not real time consuming. Then again neither is a reactor. Seems that the real work is done in the testing and adjusting and monitoring of both systems. Yet with two part I can put both parameters where I want without lowering my PH and suplementing with kalk as a lot of folks do just to keep their PH up. Yes reactor media is cheaper, but I don't know what the actual savings are for a given system.

 

OK! im here, sorry it took forever lol... but here goes:
This is a very complicated process based off of a perfect equilibrium at given pH and dynamic kinetics (nerdy stuff lol)

Ok heres what I believe the easiest way to explain this is... So you have your reactor filled with media and currently at pH 6. So hypothetically speaking at pH 6 the calcium likes to be at 380ppm. Then when the pH is down to say 5.7 then your Ca may like to be at 420ppm. Now when your pH in the reactor is at like 5.5 your Ca will be at say 450ppm. So when this calcium filled 5.5 pH effluent goes into your water it will always have Ca of 450. Now once all the water in your whole tank is synchronized at 450ppm, then the reactions inside your chamber will stop because it is at the highest point it can possibly be (given the conditions). So then say your acro decides to take up an astounding 50ppm of calcium all at once lol... your reaction is no longer at optimal equilibrium so given the conditions in the reactor (now 400ppm Ca and still pH 5.5) the media is not at equilibrium with the water so therefore it will dissolve some Ca to get the water back up to 450ppm! So to recap, as every ion of Ca is pulled from the water, one is replaced from the reaction chamber. The level of Ca in the tank is regulated by the pH the reaction chamber is kept at.

Now the technical explanation (seriously, dont read this if you hate getting headaches):
All chemical reactions sit on an equilibrium scale from 100% reactants all the way to 100% products. The dynamics of a reaction are based off of a few main aspects in order of importance: kinetic energy (temperature), pH, energy of activation, pressure, volume, concentration of products vs reactants, surface area, and lastly the rate constant which can be derived from the previously stated criteria. Rate constant is simply the change in concentration over time.
Now knowing this, a reaction will ALWAYS go to a point on the reactants to products scale where it will be at its lowest level of energy. This is one of the laws of spontaneity; stating that a reaction is always at rest when its at its lowest energy point, thus maximizing the entropy (aka randomness) of the universe (yeah yeah mumbo jumbo).
So from this you can use an equation to determine where at on the scale a reaction will sit given its known conditions:
ΔG° = -R T ln(K)
Where G is the equilibrium point, R is a constant (8.3145 J/K), T is the kinetic energy of the system, and ln(K) is the natural logarithm of the rate constant under these conditions. So from this you can determine exactly where the Calcium level will sit in the given conditions by solving for G. Now the main player to determine this level in our tanks is the pH. ~quick sidenote: In the above reaction this value is reflected in the value for K. The explanation of how it is connected will take forever so the short version is this... K is the rate, rate is determined by energy of activation over the constant R times temperature, energy of activation is determined by everything (including pH), and finally pH is regulated by a constant (8.7x10^-9 for calcium carbonate) plus the logarithm of reactant divided by product. Phew!~ So as pH changes in the chamber, so does the point where the reaction is at its lowest energy level, thus changing the dissolved concentration.
There is also another even more complicated equation to express this in terms of temperature, but as our temperature is generally pretty consistent it wouldnt do us that much help

What is interesting about this reaction also is that once it hits equilibrium in a tank it has a variable rate that is actually regulated by the rate of Ca uptake from the corals. If you get what im referring to in the last sentence, it is very interesting because its not observed very often in a chemical reaction system. <-- this is the whole dynamic kinetics part i mentioned in the beginning

 

So Dingo... I get what you are saying.... but explain to me.... it seems as if we were talking about a natural system say... like the ocean was at a PH and coral and calcium carbonate were at a equilibrium and a shift in uptake would cause a shift in PH and a shift in breakdown...

yet in the reactor we are changing PH by CO2. So the addition of CO2 to create carbonic acid to dissolve calcium carbonate into solution.... seems like that is just a seperate reaction..... then the rate at which we move water through... less ca and alk in and more out is just a matter of flow rate...

because another problem with reactors is that they lower the PH of the system and therefore can't keep ions in solution as 2 part additions at a PH of 8.3...

Is that making any sense... what am I missing?

 

OK... let me put it this way. Our consumption is 48 ppm per day... so our coral take up 2ppm per hour and our reactor puts out 2ppm per hour.

So effluent out is 452ppm and our supply to the reactor is 248ppm... that does not seem like enough of a difference to change what is in the reactor. I mean when you say the Acro takes up 50 ppm... I realize it was just an example... but ya... 450 out and 400 in.

But taken at a minute by minute and even a second by second there really never is that difference. What there is is a system at 450. The effluent is a tiny bit higher just because we intentionally dropped the PH to dissolve calcium carbonate. The supply is just a tiny bit lower.


It seems to me if there was an adjustment automatically to changes in demand.... that there would never be any difference to any reactor.... all would be set the same. X number of CO2 bubbles and X drops per minute out. CO2 flow would be automated by PH control, but effluent flow would never change no matter what because effluent concentration would change accordingly. Yet we know reactors need to be adjusted for effluent flow rate.... and please correct me if I have this wrong.

 

I am slightly confused as to what exactly you are getting at... but ill answer what I think your asking.

The effluent flow is just another way to manipulate the equilibrium position in the equation I gave above. By slowing down the flow rate you are allowing more time for the low pH to react with the media... thus instead of pH being the main factor in determining the position of the Ca dissolved, time is. The rate of dissolution is still the same, however the concentration is allowed to go higher because of the increase in time (remember K = Δconcentration/Δtime).

So using extreme examples again... Lets say the reactor is dialed into its perfect pH for the most efficient reaction to occur. Now you let it go without touching the effluent rate for a year (and your corals grew insanely fast).... Your rate of reaction would be perfect still and you are producing optimal levels of Ca for the given flow rate, however your corals are consuming more Ca than your reactor can supply with this fast flow rate. Now by slowing the flow rate just a bit you have allowed more reaction time for the dissociation to occur and thus the effluent will be able to keep up with the demand of the coral now.

I think that answers your question? if not im sorry, I havent slept for almost 24 hours and cant think straight

 

I'm working so I can't sleep.... what's your reason.

Unfortunately I never had a reactor so I do not know the ins and outs of operation. I can understand a theoretical process, but is that what actually happens... you decrease flow to put out more????

Concentrations and flow rates still deliver a specific amount. 20 parts per gallon at 10 gallons a hour is the same as 10 parts per gallon at 20 gallons a hour. Putting out less may give a higher concentration but you are decreasing flow. You are not going to deliver a higher total amount.

As far as a reactor.... you put out so many bubbles of CO2 to get a certain PH and you automate that with a PH probe and a controller. Keeping the same flow rate.... you lower PH with more CO2 and dissolve more media and raise concentration. Flow rate to the tank determines how much is going to be delivered.... you can vary CO2 and PH and concentrations inside the reactor, but you still have to deliver it to the tank. So it would seem you figure out what kind of bubble rate you need then you figure out what flow rate to deliver that over time. Do I at least have operation correct???

Then from that point.... you never touch it again because it is self regulating. CO2 is delivered automatically by the controller and the usage rate will increase. But you never have to change the effluent rate no matter how big your tank grows out and consumption increases.

Is that how it works or do you still have to monitor and keep increasing effluent rates to supply more solution as demand increases.... even though CO2 use is automated and media will always be dissolved as required.

 

My excuse is that I put this one term paper off until the last day of the semester and I had to pull an all nighter to get it done. now im just waiting for it to be time to go to class because its not worth it to go to sleep for like 2 hours... lol

But what im trying to say is that once you tweak your pH to the perfect level you will never have to touch it again. However your effluent coming out will have to be reduced in order to make the concentration higher over time.
the key player in slowing it down is that the water has more time to react with the media and can then pick up more calcium IF NEED BE <-- key word as with a slow flow it wont go above the point that the pH peaks at however it gives a grace period until the coral growth catches up to the output.