pH in a silica sand bed?

[randy holmes-farley]

Anyone ever measure the pH in a silica sand bed (say, 2-4 inches down)? I'm curious how low the pH gets.

In my CaCO3 sand bed the pH is in the mid 7's, but it is going to be maintained by dissolving CaCO3. In a silica sand bed, the pH may fall far lower, and I'm interested in knowing how low.

Thanks.

 

[Anonymous]

I can't be totally sure at that depth, but I'm willing to bet it'll fall below 5. In rural Missouri we experienced a problem with artificial ponds when we covered loam with clay and silt. We presumed that enough organic matter would accumulate on the bottom to have a truly wet anerobic zone and then heat and gases would cause a "turnover," where the pond would boil for several hours to days and be cloudy for about a week longer. After that the water would be perfectly clear with pHs sometimes as low as ~4. Then we'd add lime, drain it and start all over. Typical farmers.

P.S. There aren't any posts in your forum --^

[ February 01, 2002: Message edited by: benjemon ]</p>

 

[LeoR]

Randy,

My quick-and-dirty measurements in 2 tanks with silica sand suggest that pH should not go much lower.

Eg. in the tank with pH of 8.28, about 2" down into the silica sand bed pH is only slightly lower -- 8.14.

LeoR

 

[randy holmes-farley]

benjemon:

Actually, there are over a thousand posts in the reef chemistry forum since December when it started up. You just can't see them unless you are a registered RC member.

Thanks for the input on the pH!