07-03-2012, 06:55 PM
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Originally Posted by shady07
Cool cool, so i guess having regular play sand as a substrate is fine for plants. But i've read some conflicting reports that some plants cannot root in sand becasue the sand "crushes" the roots and they cannot "breathe". Is this just a myth or is there some truth behind this.
I would suspect what the author/source means is the compaction of sand. Any substrate can compact if not looked after or if there is something wrong. And the finer the substrate, the faster this can occur. And if this does occur, it will kill the plant roots--you see it as black, as are the roots.
In the aquarium we can deal with this by not having too deep a substrate, by having a good complement of substrate-rooted plants, by keeping Malaysian Livebearing snails, and by poking or stirring the sand periodically. All of these may not be needed in every situation.
The poking/stirring of the sand I never do, because the other factors handle it adequately. The MLS burrow throughout the substrate, keeping it loose and "fresh," so water carrying oxygen is better able to percolate through it. And the tank water must be able to pass through the substrate. The plant roots assist by releasing a lot of oxygen via photosynthesis. As plants photosynthesize they release oxygen, but a considerable proportion of this is through the roots. When these are in the substrate, they feed oxygen into the surrounding substrate; various bacteria use this oxygen to further break down organics. Maintaining a not-too-deep substrate allows this to occur over more of the substrate, limiting the "dead spots" as they are called. These latter are actually essential however, provided they do not overpower the substrate.