Quote:
Originally posted by aquaticsdeptleader
...my conclusion is that what the sand is made of wont dictate amounts of algae. so out side of particle size does it really matter what sand we use?
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Hey Jim, prolly not much of a problem, although certain types of river sand contain organosilicates that are much more soluble than plain silicon dioxide. In actuality, hardness has nothing to do with the availability of the silica/silicate for
diatom blooms (the biggest problem for aquaria use), but rather it's solubility. Glass as such is prolly less soluble than river sand (somewhere on the level of 3mcg/l, quite INSOLUBLE) and accounts for its use in analytical chemistry (so that it does not react with the substances being tested). The multitude of different silicates found in differing grades of river and beach sands will definitely provide more silicate to the water column, so I would think that a mined source of relatively pure sand would be desirable as opposed to river sand, or any sand contaminated with feldspars, etc.
Particle size is prolly the largest single determinator in selecting a substrate. The use of calcium carbonate based sands (aragonite or calcite) would be preferential, as they both mimic both Caribbean and Indo-Pacific substrates more closely. Although many folks use a fine grade (sugar sized) of sand such as Aragamax or Southdown, It would prolly be best to see a multitude of particle sizes from 2mm down to 0.5mm with some occasional larger particle sizes for creatures that require them (for building burrows, etc). Dr. Ron has several articles on sandbed particle sizes, as well as those by Rob Toonen and a few other folks (I am starting to wonder about the impartiality of Bob Goeman's work...
). Basically we don't want something down to the size of silt, but anything larger than sugar sized substrates begin to dramatically reduce surface area available to colonizing bacteria/algae, etc. The ability of carbonate substrates to buffer the water column does count towards its selection as the substrate of choice, however, this function is greatly reduced by the presence of a biofilm of benthic microorganisms by the time the tank begins to mature, and although creatures that digest this biofilm off the substrate (i.e., sea cukes, etc.) may temporarily remove this film, I am not sure that this contributes in a major way in view of the huge utilization of Ca and Alk by
hermatypic corals in a closed system.
To answer your question, yes, SIZE DOES MATTER...
, but the substrate of choice would still be sugar-sized aragonite, possibly a mixture of several granule sizes, but mostly those of the 1 to 2 mm size. I am sure that several folks will post links to the literature on this.
Hope this helps.
