Need help tuning calcium reactor

Dave-T · Mar 16, 2023

I'm dosing 80 liters/day out of my calcium reactor into an 8 month old 240 gallon tank/350 gallon system. Mostly LPS, some softies and small SPS frags. A 5 inch clam.

When I started running the calcium reactor a few months ago, I could maintain the alkalinity by dosing 30 L/day, but I've had to gradually increase it up to the current 80 liters/day. I'm not sure if this is reasonable or if my effluent is off.

I took some measurements of the calc reactor effluent: 6.8 PH, 23.8 dKh, 550 PPM calcium, all using Hanna. (I diluted the effluent 50/50 with RO water to measure the alk, but not the calc.)

My system dKh is pretty steady between 8 and 9 (I track it with a GHL KH Director, but verified with Hanna.) But my calc has been pretty steadily dropping, I last measured it yesterday and it was at 314.

So my questions are:

* Are those numbers reasonable for my effluent chemistry? I would have thought the calc would be higher.

* Does it make sense that my calc reactor can maintain alk but not calc? I could start dosing calc, but I didn't think that was necessary with a calcium reactor.

* Isn't the amount I'm dosing high, for such a young tank? 80 liters of effluent per day?

Thanks!

Edit: you may want to know my mag - it's at 1310, according to Hanna.

Dennis Cartier · Mar 16, 2023

Your numbers do look a bit off. Your tank calcium sounds really low. How are you measuring it? I would retest that parameter.

Your effulent also looks a bit unbalanced. When calcium and alk get used, it is at 2.8 dKH per 20 ppm calcium, so I would expect a CaRx to provide supplementation in a similar ratio. So based on your values, your effulent is high in calcium or low in alk. Which is the exact opposite of what you would expect with low tank calcium.

Dave-T · Mar 16, 2023

I did retest. I’m testing with a Hanna checker. Thanks for the info on the dkh per calcium consumption ratio. That’s helpful. But what are typical values for effluent?

Dennis Cartier · Mar 16, 2023

Dave-T said:
I did retest. I’m testing with a Hanna checker. Thanks for the info on the dkh per calcium consumption ratio. That’s helpful. But what are typical values for effluent?

It depends on the calcium reactor, and how it is adjusted. Typically the pH of the water column inside the reactor impacts the effulent strength. 25 dKH is about the lowest you would want to see. Your calcium reactor should be able to produce effluent as high as 40 - 45 dKH. Secondary chambers are a great way of getting stronger effluent.

I operate a saturation style reactor where CO2 is dissolved until the water column reaches saturation and can't hold anymore. My effulent is 90 dKH. Again this is due to the different reactor type.

If you want stronger effluent, then I would suggest a lower pH. Reading some of the tuning threads would also be a good idea.

For your calcium measurements are you using a pipette to get an accurate water sample? The Hanna calcium checkers have a reputation of being difficult to get accuracy from unless you can get a very accurate volume sample.

Dennis Cartier · Mar 16, 2023

Here is a thread where I go through my views on effluent strength. Though the thread was mainly focused on minimizing the pH drop caused by a CaRx.

New CaRx - Huge hit time system ph - Help?

I have a 200g completely stocked wall to wall SPS system. As of Friday I was dosing a gallon of full strength Kalkwasser every 3 days as well as 300mL/day soda ash/Calcium 2 part via a DOS. This was becoming too much work so I decided to set up a GeoReefs 618 CaRx. My normal system pH range...

www.reef2reef.com

Dave-T · Mar 16, 2023

Dennis Cartier said:
It depends on the calcium reactor, and how it is adjusted. Typically the pH of the water column inside the reactor impacts the effulent strength. 25 dKH is about the lowest you would want to see. Your calcium reactor should be able to produce effluent as high as 40 - 45 dKH. Secondary chambers are a great way of getting stronger effluent.

I operate a saturation style reactor where CO2 is dissolved until the water column reaches saturation and can't hold anymore. My effulent is 90 dKH. Again this is due to the different reactor type.

If you want stronger effluent, then I would suggest a lower pH. Reading some of the tuning threads would also be a good idea.

For your calcium measurements are you using a pipette to get an accurate water sample? The Hanna calcium checkers have a reputation of being difficult to get accuracy from unless you can get a very accurate volume sample.

I’m using a 10ml syringe to measure the water. This is my reactor, it is two chamber:

Super Reef Octopus CR5000D 8" Calcium Reactor

Maintain the calcium and alkalinity in your reef tank with a high performance dual chamber calcium reactor from Reef Octopus. The Super Reef Octopus CR5000D 8" Dual Calcium Reactor has all the performance you've come to expect from the expert series of Super Reef Octopus. Rated for aquariums up...

www.bulkreefsupply.com

So I can adjust the PH to get stronger effluent, but I’d like to understand why my Calc to alk ratio is so low. As it is, unless I want to drive alk very high, it seems like I’ll need to dose Calc on top of using the reactor. Isn’t that weird?

Dave-T · Mar 16, 2023

Double post…

Dennis Cartier · Mar 16, 2023

I would suggest picking up a manual titration calcium test to double check your calcium results. Salifert makes a good one.

I don't use the Hanna Ca tester, but as I mentioned I have heard that you need to use a pipette to get reliable results out of it.

Dave-T · Mar 16, 2023

Ok, thanks. I’ll try the Salifert. I’m pretty careful about my measuring, but if the Hanna is off, then that would explain things. We will see! I’ll report back after I try measuring with Salifert.

Randy Holmes-Farley · Mar 17, 2023

This article may be useful:

A Guide to Using Calcium Reactors

http://reefkeeping.com/issues/2002-05/sh/feature/index.htm

Randy Holmes-Farley · Mar 17, 2023

And this guide and calculator:

Calcium Reactor Setup Help

Dave-T · Mar 18, 2023

Ok, I verified with salifert. My effluent is 550ppm Calc, 24dKH alk. So my Calc to alk ratio is low out of my reactor. Someone suggested I try different media in my reactor. I’m going to try that.

Randy Holmes-Farley · Mar 19, 2023

Dave-T said:
Ok, I verified with salifert. My effluent is 550ppm Calc, 24dKH alk. So my Calc to alk ratio is low out of my reactor. Someone suggested I try different media in my reactor. I’m going to try that.

I don't think a faulty media explains anything, and as best I can tell, your measurements suggest way too much calcium per alk coming out of it, which IMO, is a testing issue (perhaps faulty calcium testing in the tank).

Calcium 314 --> 550 ppm ought to be accompanied by a rise in alk of about 35 dKH to 44 dKH.

X-37B · Mar 19, 2023

What media are you currently running?

Dave-T · Mar 19, 2023

90's reefer said:
What media are you currently running?

Aragonite: https://www.bulkreefsupply.com/caribsea-arm-reactor-media-extra-coarse.html

Dave-T · Mar 19, 2023

Randy Holmes-Farley said:
I don't think a faulty media explains anything, and as best I can tell, your measurements suggest way too much calcium per alk coming out of it, which IMO, is a testing issue (perhaps faulty calcium testing in the tank).

Calcium 314 --> 550 ppm ought to be accompanied by a rise in alk of about 35 dKH to 44 dKH.

Ok, but all I can say is that I was extremely careful with my testing, testing multiple times and with two different kits (Hanna and Salifert). All tests agreed. Just to be clear - I’m not you understood me, or perhaps I am not understanding you. I got 314 calcium in my system, the 550 number was from my reactor effluent.

Randy Holmes-Farley · Mar 20, 2023

Dave-T said:
Ok, but all I can say is that I was extremely careful with my testing, testing multiple times and with two different kits (Hanna and Salifert). All tests agreed. Just to be clear - I’m not you understood me, or perhaps I am not understanding you. I got 314 calcium in my system, the 550 number was from my reactor effluent.

Correct, so the purported rise in calcium is from 314 to 550 ppm. A rise of 550-314 = 236 ppm MUST be accompanied by a rise of about 33 dKH in the effluent, from 9 to 42 dKH.

You report the effluent alkalinity is 24 dKH, which it migth be. Assuming that is correct, then the alk rise is 24-9 dKH = 15 dKH.

If that 15 dKH rise is correct, then the calcium rise can only be about 107 ppm, not 236 ppm.

Dave-T · Mar 20, 2023

Randy Holmes-Farley said:
Correct, so the purported rise in calcium is from 314 to 550 ppm. A rise of 550-314 = 236 ppm MUST be accompanied by a rise of about 33 dKH in the effluent, from 9 to 42 dKH.

You report the effluent alkalinity is 24 dKH, which it migth be. Assuming that is correct, then the alk rise is 24-9 dKH = 15 dKH.

If that 15 dKH rise is correct, then the calcium rise can only be about 107 ppm, not 236 ppm.

Ok, that clears up a few things, thanks! So it is not possible for a calcium reactor to produce an effluent where the ratio of alk to calcium is other than 2.8dKh per 20ppm calcium. So that would imply that my testing is faulty. I just don't know where I could have messed up my testing, I've tested both calc and alk using multiple tests (Hanna and Salifert for calc, Hanna and GHL KH Director for alk), and they all agree. Clearly I need to get my testing accurate before I can draw any conclusions to act on. I ordered the Red Sea calc and alk tests, I'll see what I get from those.

Randy Holmes-Farley · Mar 20, 2023

Dave-T said:
Ok, that clears up a few things, thanks! So it is not possible for a calcium reactor to produce an effluent where the ratio of alk to calcium is other than 2.8dKh per 20ppm calcium. So that would imply that my testing is faulty. I just don't know where I could have messed up my testing, I've tested both calc and alk using multiple tests (Hanna and Salifert for calc, Hanna and GHL KH Director for alk), and they all agree. Clearly I need to get my testing accurate before I can draw any conclusions to act on. I ordered the Red Sea calc and alk tests, I'll see what I get from those.

If you use dolomite instead of aragonite, a bit more than usual magnesium is released in place of some of the calcium, and some folks do that to maintain magnesium, but it is not possible to release more calcium than 20 ppm per 2.8 dKH.

Testing issues are common. Some of the controllers have issues when reagent starts to get low.