Originally Posted by Ohsogreen

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Buffalosoulja... Yes, the sand is trapping nutes. DE (Diatomaceous Earth) will provide a physical barrier to deter and kill gnats - without trapping nutes. Most decent garden centers & hardware stores carrier it. It will kill anything that crawls or flys.
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I'd spoon off the sand and replace it with DE mixed 1/2 & 1/2 with some new soil or spaghum peat moss.
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Hope this helps...
Keep it Real...Organic....