Koi-lo wrote:

"Cliff L" wrote in message
oups.com...

It's more natural than a plain glass bottom.


True, but I wonder how common a gravel subtrate is
for aquarium fish in the wild, as opposed to mud or
larger river stones.

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That depends where you live. Here the river bottoms are covered with
stones and pebbles of various sizes, the soil washed downstream ages
ago. On L.I. the ponds and inlets were sand, pebbles and stones. The
lake here has a mud and rock bottom.

If memory serves me rightly, the bottom of the Thames is squidgy mud
with the odd bit of stone/gravel but predominately mud...used to get
stuck between your toes - lol. It was a long time ago when I was mad
enough to swim in there but I'm pretty sure that it won't have changed
much....