Trouble tuning my Geo618 calcium reactor

[randyman]

Hi All -

I'm having trouble tuning my Geo 618 Calcium reactor on my 120 Gal. Alkalinity keeps creeping up until I hit 12 DKH. If I keep the reactor on, it will inch further.

Media used:
Magnesium from BRS: http://www.bulkreefsupply.com/korall...late-1-kg.html
ReBorn Calcium Reactor Media from Two Little fishes

combination of both media is added to the Geo 618 fill line
3/4 of media is ReBorn and 1/4 is the Magnesium

Current Calcium reactor settings:
pH probe setting is at 7 with 0.1 hysteresis
Effluent date is 70mL/minute

With two part dosing I can get the tank to 10 dKH and and calcium at 420. After I turn on the reactor the alkalinity starts creeping up and within a few days it's up to 14 dKH. I've played with the pH and the effluent rate and the setting I have now provides the slowest rate of increase in alkalinity. At the same time the Calcium drops back down to 380. Magnesium stays fairly constant at 1300/ppm before and after the calcium reactor is running. I also do a 3 gal water change daily. Mix is Tropic Marin Pro Reef.

I don't have that many SPS/LPS corals in my tank now, 8 smallish frags.

Does anybody have any suggestions for me keep the alkalinity from running away? This has been a long process for me as I have to wait 4-5 days for the alkalinity to decrease back to 10ish before I try a new reactor pH level and effluent rate.

Any suggestions would be greatly appreciated.


Thanks ...

[pirate2876]

I have the same reactor as you, and I have had the same problem as you as well.

Marc from Melevreef.com referred to these as alkalinity reactors, rather than calcium reactors. I think that was spot on. I also think that is why it is so beneficial to SPS tanks for the constant alk.

The first thing I would do is see try and lower the effluent rate through the reactor. Mine is steady at about a drip every 2-3 seconds. A drip, not a constant stream. The effluent should be pretty concentrated.

If that doesn't help, try to decrease the amount of media in the reactor. You might just have too much for your needs if the production rate is higher than the consumption rate. I have a 65g tank packed with SPS, and I dont need to have my reactor more than half full. I also mark the where the media is when full. Slowly, but surely, the media shrinks in size.

I would also aim for a PH of 6.4-6.5 in the chamber for larger media. I believe you can run a higher PH with smaller media, but I use the bigger ARM media, so at 6.4 the CO2 is shut off by the controller.

How old is the probe in the chamber? I like to recalibrate the probe everyone once in a while as well. Just as a precaution.

Once you get that dialed in, you will be good to go though. It is a good amount of trial and error, but what isn't like that in this hobby?

[Bogg]

you don't have the demand yet turn it way down

[diegoluv]

I had the same problem with my first calc reactor too. Throttle back the effluent until you get a steady DKH. Once thats stable you can adjust the media for calcium concentrate. If you dont have a heavy SPS bioload it's really hard to dial in both the alk and calc in my experience.

[rob.d]

I ran a GEO 624 and had similar issues in a stocked SPS tank, keep the effluent flow at 50ml per minute and like pirate states keep reactor ph around 6.5 and the size of the bubble going into that reactor is also a big factor and psi try to keep outlet psi into GEO around 6psi, 9 psi would be a bigger bubble and it would affect KH. I ran a carbondoser electronic regulator and I'm not familiar with a manual carbon regulator and can't give you a bubble count.it was hard to dial it in but stable after you figure out your tank demands
Hope that helps a little

[randyman]

Thanks for taking time to give me some helpful tips! I appreciate you taking time out of your busy schedules.

I"m thinking I have too much media as I started with the pH at 6.5 and then stepped up and down 0.2, down to 6.0 and up to 7.0. Each timing starting with the effluent flow low then increasing. As I backed down the effluent rate, the calcium would drop down to 350.

Wanted to get the reactor working nicely before I loaded up with SPS and LSP, can't stand watching corals die and throw money away.

Cheers,

Randy