bjgf15
Mon, 18th Oct 2010, 05:37 PM
I thought I'd share the results of a brief preliminary experiment I conducted on the affects of mature sand beds on Phosphate levels within an aquarium.
The experiment was spurred by the fact that I had a persistent algae problem on my sand bed (and some of my rocks close to the sand), despite having a large, efficient skimmer, great flow, carbon reactor, large phosban reactor, UV sterilizer etc... And also the fact that Dr. Ron Schimek preaches sand beds as the MOST important part of any reef tank in one of his books.
Now, the smart money would be on me overstocking/overfeeding my tank. And while the tank is well stocked and fed, water parameters always were ALWAYS great, so hence my experiment...
I had access to a very accurate colorimeter which can measure PO4 to 0.001 ppm! So I decided to put it to good use.
I tested water column water and pore water (from within the sand bed) of 3 mature (2+ yrs) reef tanks. I found very low (0.02 ppm or less) PO4 in the water columns of the systems but found highly elevated PO4 levels in the pore water (0.05ppm+) at the bottom of the sand beds. The more heavily stocked systems had higher PO4 in the sand. High PO4 levels also appear to be correlated with the depth of the sand bed.
What I can conclude from this little experiment is that sand tends to leach PO4 (and presumably other organics) over time as waste is broken down by microbes. Skimmers are designed to remove organics BEFORE they are broken down into small molecules such as PO4 and as a results skimmers don't remove PO4 very effectively. This can trigger blooms of undesirable algae and/or cause you to go through expensive media such as GFO much quicker than need be.
I have since removed the vast majority of sand from one of the tanks (I like the look of sand so I have left 1/4" on the bottom) to see whether this is effective in stopping the elevated PO4 levels in the sand.
The experiment was spurred by the fact that I had a persistent algae problem on my sand bed (and some of my rocks close to the sand), despite having a large, efficient skimmer, great flow, carbon reactor, large phosban reactor, UV sterilizer etc... And also the fact that Dr. Ron Schimek preaches sand beds as the MOST important part of any reef tank in one of his books.
Now, the smart money would be on me overstocking/overfeeding my tank. And while the tank is well stocked and fed, water parameters always were ALWAYS great, so hence my experiment...
I had access to a very accurate colorimeter which can measure PO4 to 0.001 ppm! So I decided to put it to good use.
I tested water column water and pore water (from within the sand bed) of 3 mature (2+ yrs) reef tanks. I found very low (0.02 ppm or less) PO4 in the water columns of the systems but found highly elevated PO4 levels in the pore water (0.05ppm+) at the bottom of the sand beds. The more heavily stocked systems had higher PO4 in the sand. High PO4 levels also appear to be correlated with the depth of the sand bed.
What I can conclude from this little experiment is that sand tends to leach PO4 (and presumably other organics) over time as waste is broken down by microbes. Skimmers are designed to remove organics BEFORE they are broken down into small molecules such as PO4 and as a results skimmers don't remove PO4 very effectively. This can trigger blooms of undesirable algae and/or cause you to go through expensive media such as GFO much quicker than need be.
I have since removed the vast majority of sand from one of the tanks (I like the look of sand so I have left 1/4" on the bottom) to see whether this is effective in stopping the elevated PO4 levels in the sand.