Calcium Reactor Media

I'm using Caribsea GeoMarine substrate in my calcium reactor.  I was told by someone that using this material would lead to high phosphates.  So I went looking for info.  Greg Hiller did a study found here:  http://www.advancedaquarist.com/issues/april2003/short.htm In it he tested Koralith, ARM and a locally quarried limestone which he had been using.  He didn't test Geomarine.  So I decided to repeat his experiments using GeoMarine and ARM as a comparison to his results.  I also tested Caribsea Seafloor substrate.  I dissolved 10 grams of substrate in 25 ml of concentrated HCl.  Then adjusted the pH of this solution back to 7 by addition of KOH.  The samples were then diluted to 1 liter and analyzed for phosphate using a Hach 2000 spectrophotometer.  The samples were then diluted 10:1 and analyzed for calcium.  In this manner a Ca:PO4 ratio can be calculated (higher numbers are better).

Here's the results:

Geomarine:  1.76 mg/l PO4, 3640 mg/l Ca giving a Ca:PO4 ratio of 2068

ARM:  0.82 mg/l PO4, 3600 mg/l Ca giving a Ca:PO4 ratio of 4390

Caribsea Seafloor:  0.83 mg/l PO4, 3840 mg/l Ca giving a Ca:PO4 ratio of 4626

So in fact there is almost twice as much phosphate added to my tank water using Geomarine compared to ARM (or Seafloor).  But is it really significant?  Dr. Shimek did some analysis of "average" aquarist feeding habits found here:  http://reefkeeping.com/issues/2002-04/rs/feature/index.htm  He found that the average person adds 0.0086 grams of phosphorus to his tank per day due to feeding.  This is equivalent to 26.3 mg of Phosphate (PO4) per day.  My calcium reactor adds 0.4 meq/l alkalinity per day to my tank.  That is equivalent to 3780 mg of calcium.  For every 2068 mg of calcium I'm adding 1 mg of PO4 using Geomarine.  So my calcium reactor is adding 1.83 mg of PO4 per day.  That's not much compared to the amount added from my food.  And my tank water has undetectable PO4 even using the Geomarine.  The other interesting thing is that the Seafloor material tested to be almost exactly the same as the ARM media.  Both media's are sold by Caribsea (as is Geomarine).  The Seafloor substrate looks very similar to the ARM media except the Seafloor is smaller sized.  I would think if pressure drop isn't a concern in your reactor then using the cheap old Seafloor material would be a very good option.

Thanks to Cody Pearce for the ARM media and Mark Peterson for the Caribsea Seafloor substrate.

Jon,

I have been using seafloor in the ractors we build I have tryed to explain to many people that its a great way to save money and the arm is 2 to 3 times the cost. Thanks for the results....