RO/DI Water into Calcium Reactor

[John Freeman]

This is a Randy question.

I have searched the entire web and haven't found this addressed. Typical setup for a Calcium Reactor uses some kind of pump (usually a parasitic) to pump water through a Calcium Reactor. I am wondering if there is any reason one can not push top off water from one's RO/DI filter into the Calcium Reactor. (Yes I mean Calcium Reactor NOT a kalkwasser reactor.) I have been successfully running a Calcium Reactor for years. Recently my parasitic pump wore out an now that I am retired am trying to cut back on expenses.

I have a PH controller on the Calcium Reactor to maintain PH. My system uses 2-3 gallons of top off water per day. I have always set up the parasitic pump to run about 1.5 drops per sec. which works out to about 2.2 gallons per day through the reactor. So the amount of top off water is fairly close to what I have pushed through the reactor all these years. I use an automatic top off system to add RO/DI water to my system. I am considering feeding this top off water through my Calcium Reactor.

My question is, is there any reason chemically that feeding RO water into the reactor would result in improper function of the reactor? The PH controller will still maintain the 6.6 to 6.7 PH level I have always used. The flows are about the same. RO water is very reactive and I would think that it would aid the dissolving of the media.

 

[Randy Holmes-Farley]

What you are suggesting may work (certainly would work to some extent), but there may be unforeseen issues and the pH likely needs to be different and probably lower than in the seawater because calcium carbonate is more soluble in seawater than in fresh water (at the same pH). I calculated in the second article below that if you did this with 3.5 atmospheres of CO2 (e.g., it is pressurized, not just allowed to bubble in) you could get to about 30 dKH in alkalinity so it could be similarly potent to the way CaCO3/CO2 reactors are normally used.

So I'd be curious to see what happens if you try, but it is not a slam dunk that it will work with the same equipment.

I discuss it tangentially here:

The Many Methods for Supplementing Calcium and Alkalinity - REEFEDITION
https://www.reef2reef.com/blog/the-many-methods-for-supplementing-calcium-and-alkalinity

and here:

Chemistry And The Aquarium: Calcium Carbonate As A Supplement ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/2002/7/chemistry

 

[John Freeman]

Randy, thanks for the input. I am going to give a try for a few days. Haven't got much to loose at least until I can find a replacement pump I can afford. I have dropped the PH controller setting to about 6.5. I tested salinity and Calcium level a hour or so ago and it was 1.15 salinity and about 180ppm on the calcium. Will report again once I get the salt water purged from the reactor.

 

[Randy Holmes-Farley]

Randy, thanks for the input. I am going to give a try for a few days. Haven't got much to loose at least until I can find a replacement pump I can afford. I have dropped the PH controller setting to about 6.5. I tested salinity and Calcium level a hour or so ago and it was 1.15 salinity and about 180ppm on the calcium. Will report again once I get the salt water purged from the reactor.

180 ppm calcium in the effluent? Was it clear? Particulates in it will give a false high reading, but if that is real dissolved calcium, that's quite a lot! Alk should be about 25 dKH, and so it's as potent as normal use.

 

[John Freeman]

Randy, yes the water was clear when I took readings on 3/11.

I have been waiting a few days to see how things stabilized. I have had the PH controller set to maintain a PH of 6.6 now for the past week. All my top off water is flowing through the reactor. Did a calcium test this morning and found that the effluent Cal level had dropped to 50 ppm. The Alk measured 8.3 dKH and using my TDS meter the hardness measured 200 ppm. The salinity was 1.00 so almost all the residual salt has purged from the reactor. Water was perfectly clear. All measurements were done using Salifert Calcium and Alkalinity test kits. Both kits state they are usable with both Salt and fresh water. FYI, the calcium reactor is a Reef Octopus dual chamber unit. I would estimate the amount of water in it is around 4 gallons. Each chamber is filled with crushed coral.

I had tested my tank calcium levels on 3/11/16 and had Calcium level of 425. Alk was 2.73. Mag level was about 1280. Tank today is testing 415 and 2.15 so levels have dropped a tad. PH level in tank reads 7.98 which is very typical for my tank. The tank is a 150 gal tank with 50 gal refugium. I have numerous large polyp and hard corals so my calcium consumption is fairly high.

After doing my tests this morning I have lowered the PH setting of the PH controller to about 6.4. Will monitor over the next week to see if lowering PH raises the Cal levels any.

 

[Randy Holmes-Farley]

Randy, yes the water was clear when I took readings on 3/11.

I have been waiting a few days to see how things stabilized. I have had the PH controller set to maintain a PH of 6.6 now for the past week. All my top off water is flowing through the reactor. Did a calcium test this morning and found that the effluent Cal level had dropped to 50 ppm. The Alk measured 8.3 dKH and using my TDS meter the hardness measured 200 ppm. The salinity was 1.00 so almost all the residual salt has purged from the reactor. Water was perfectly clear. All measurements were done using Salifert Calcium and Alkalinity test kits. Both kits state they are usable with both Salt and fresh water. FYI, the calcium reactor is a Reef Octopus dual chamber unit. I would estimate the amount of water in it is around 4 gallons. Each chamber is filled with crushed coral.

I had tested my tank calcium levels on 3/11/16 and had Calcium level of 425. Alk was 2.73. Mag level was about 1280. Tank today is testing 415 and 2.15 so levels have dropped a tad. PH level in tank reads 7.98 which is very typical for my tank. The tank is a 150 gal tank with 50 gal refugium. I have numerous large polyp and hard corals so my calcium consumption is fairly high.

After doing my tests this morning I have lowered the PH setting of the PH controller to about 6.4. Will monitor over the next week to see if lowering PH raises the Cal levels any.

So now the effluent is a lot less potent than saturated limewater, and probably won't keep up with demand in most tanks. It will be interesting to see how much you can get from it.

 

[John Freeman]

The attached files will give you some idea of our coral load.

 

[Randy Holmes-Farley]

That should have pretty good demand from the coralline alone. Are you tracking tank alk?

 

[John Freeman]

That should have pretty good demand from the coralline alone. Are you tracking tank alk?

Yes, I always test the Alk levels when I test CA to make sure it is balanced. It runs pretty well balanced per your recommendations.

Today I retested effluent again after having the PH controller set to 6.2 for the past week and calcium was measuring about 130ppm. The Alk of the effluent was off the chart above the level of my test kit's capability which I found puzzling.

So with the lower PH setting on controller I am getting higher numbers. The CO2 in the reactor doesn't fully dissolve so there are always bubbles of CO2 circulating inside the reactor. The controller keeps the solenoid valve that controls the CO2 on nearly constantly which tells me I am consuming large amounts of CO2 gas to try to keep the PH that low with the constant flow of RO/DI water through the reactor. I think the evaporation is using more RO/DI makeup water that I originally estimated.

My tank measured 390 ppm cal, Alk was 1.65 meq and PH was 7.96. This is down from last weeks reading of 415 and 2.15 so levels have dropped fairly significantly this week.

 

[Randy Holmes-Farley]

At 1.65 meq/l, the tank is getting seriously deficient in alk. Id look to use some other methods instead of, or in addition to the reactor.

 

[John Freeman]

t 1.65 meq/l, the tank is getting seriously deficient in alk. Id look to use some other methods instead of, or in addition to the reactor.

I was in basement mixing up a Baking Soda drip about the time you posted this.

 

[John Freeman]

Wanted to do an update after a few weeks of trying this experiment. Overall it was a failure. While water tests with PH controller set to 6.3, showed effluent calcium levels to run a fairly consistent 130ppm my calcium and alkalinity levels continued to drop very quickly after every addition of Cal and Alk supplements. Another issue was that the CO2 being added to the reactor were circulating as large bubbles. When using salt water when the CO2 hit the re-circulation pump it would produce micro bubbles because of the higher density of the salt water. With fresh water, even though the PH meter showed a PH of 6.3, I don't think it was doing an efficient job of dissolving the CO2 into the water.

Ultimately I was able to find a used Blue White Flexflo A-100 Series Model 130-6 Pool Chlorinator Peristaltic Pump on Ebay for $40. This pump in nice in that it has a built in timer that allows one to adjust the percentage of time the pump is running to regulate the flow through the reactor. New they are a bit pricey but I would recommend it. Very solidly built.

 

[Randy Holmes-Farley]

Thanks for the update!