Arcuritech - 21-8-2012 at 15:13
I have hermit crabs and the sand I tend to use in their tank is made of CaCO3 in stead of SiO2. Thinking "Hey, there's a
convenient source of Calcium Ethanoate!" I let ~20g of it soak in distilled white vinegar for a week. Two days ago I noticed that fuzzy blotches had
formed in it. Curious about what would happen next I left it undisturbed and now there is a sizable amount of the familiar fuzzy "bread mold"
floating in the solution!
My question is: What could it be metabolizing? It can't be photosynthesizing because it has no Mg to make Chlorophyll with and can't possibly be
eating the Calcium Ethanoate, right?
[Edited on 21-8-2012 by Arcuritech]
Yo-Yo - 21-8-2012 at 22:40
Molds can live on almost any carbon source. I have seen mold in 10 mM triss-buffer!
bbartlog - 22-8-2012 at 18:17
Acetic acid seems like it could be a food source for some organisms. As for CaCO3 *sand* being free of Mg, ha! I bet even reagent-grade CaCO3
typically has traces of Mg in it. Any natural source (limestone, seashells, eggshells) I bet would have 1% MgCO3 or more.
Arcuritech - 22-8-2012 at 18:35
@Yo-Yo: Wow, I had no idea mold could do that! 
@bbartlog: The sand does appear to be limestone as well.
@All: Thanks for the help!
White Yeti - 10-9-2012 at 12:41
I've seen the same thing. I've actually seen mold grow in zinc acetate solution(!) Copper acetate can usually resist such attacks because copper is
extremely toxic to most fungi. Nevertheless, the concentration of zinc should have been high enough to inhibit any kind of decomposition. After this,
I was forced to convert all the zinc acetate solution I had (for galvanizing) to zinc carbonate which can be stored indefinitely to the best of my
knowledge.
zed - 22-9-2012 at 12:57
Acetic acid generally doesn't spoil. Too acetic. Vinegar keeps quite well without refrigeration. Bugs, aka micro-organisms, generally can't utilize
it as an energy source.
Neutralize the acid with Ca however, and the carbon present might suddenly become "lunch-able".