Substrate question

Forgive me my ignorance, but after hearing about vermiculite for all 
that time I've been subscribed here, I finally decided to ask: What 
is it actually, and what good (or bad) does it do in a plant tank?
Where can it be bought (garden-supply  store, pet store, etc)? 

I'm contemplating rebuilding my 50 litre tank (15 gal). I was 
thinking I would go with 1 cm of potting soil covered with 2-3 cm fine 
sand (1 inch= 2.54 cm). The lighting is currently a single 11W 
compact fluo - I will upgrade it to 16W soon and then will perhaps 
even double that. Filtration is none. I am thinking about adding DIY 
CO2 (after I change the substrate). 

Does this sound reasonable? Especially, is the substrate mix ok?



Jan Fidrmuc

CentER for Economic Research
Tilburg University
P.O.Box 90153
5000 LE Tilburg, 
The Netherlands

Phone: +31-13-466-2678, +31-13-466-8221
Fax: +31-13-466-3066
Email: J.Fidrmuc at KUB_NL