sand isnt expensive if you know where to look. i just got 50 lbs of AquaQuartz pool filter sand for $5.50 at Ace hardware. the sand looks great in my 37 and it sinks pretty fast, even though its pretty fine (.45-.55 mm grain size). it didnt need to be washed for long, and looks great, the corydoras are very fond of it.
also, my corydoras never had any problems with my gravel in my 20 gallon. they seem to like the sand better though...
also, my corydoras never had any problems with my gravel in my 20 gallon. they seem to like the sand better though...