ghbrewer;935038 wrote: Heath brings up are really good point that I am sure many experienced aquarists share, that is you really should try and steer clear of anything that is not made expliclty for aquarium use. This is a very common sense approach to reef keeping, in that you don't always know if what you are getting will cause more harm than good to your aquarium. With that said, there are many people who have used play sand in their DTs and said that they liked it. While there are others that have said that it ended up being more of a pain in the a** than anything else.
Just as it seems you are aware, silica based sands will provide little to no buffering capacity, as they contain little to no calcium carbonate. As stated in another thread, I would not rely on a DSB to make up for bad husbandry or less than optimal PH swings and calcium levels. These items should be controlled through the use of regular testing and purpose built, tried and true practices such as using a calcium reactor or dosing regimen.
Things to consider:
The majority of silica based sands available to consumers is man-made and is likely to contain a large amount of impurities. While silica based sands won't likely release silicates into the water column in and of itself, there is a good chance that there might be silicate in the packaging due to the production process as well as other things such as heavy metals. There are ways to test silica sand for impurities such as silicates and heavy metals, but IMO the whole thing is just not worth the trouble unless you are just dead set on using it. Crushed coral and aragonite substrates are taken directly from the ocean and are much less likely to contain contaminates that could be detrimental to your aquarium and its inhabitants. While it is more costly, you are not gambling so much with what you may be putting into your system.
Other issues with using silica based sands have to do with the particle shape and size. Silica based sands are more jagged and sharp (more easily traps detritus) than their aragonite and crushed coral alternatives and tend to be. While a few independent studies have shown little difference in the capabilities of silica and calcium based sands to culture beneficial bacteria, calcium based sands are proven through years of successful use. In regards to particle size, silica sand is typically of a much finer gradation and when used in a display tank can easily be blown around by power heads (especially in high flow environments like those that house SPS).
No matter what substrate you use (if any at all), proper husbandry and maintenance is a must. I would also suggest you invest in a good clean up crew (CUC), as they will assist you in maintaining your substrate. I also believe in siphoning of the sand bed during each and every water change, replacing any substrate that is removed with fresh substrate. I have heard from reputable sources that you should expect to remove and replace around 25% of your substrate every three months, theoretically replacing all of it over a year.
Of course, all of this is what I have encountered in my own research and heard from others. I am definitely not an expert and do suggest you do your own research prior to incorporating anything into your own system.
