wrote:

I am considering ordering Carib-Sea Amazon Basin gravel at
great expense. I live in Greensboro NC.

Can't think of anything else except that it seems logical it might be
the gravel.

However, I do have a suggestion for a great planted tank gravel:
Profile Aquatic Plant Soil. You can get it at home centers like Home
Depot. It's also sold under other variety names for a little cheaper
like "Turface" and "Shultz Soil Conditioner," but the particle sizes
can vary to almost dust-like in these other varieties. Profile is a
lot like Seachem Flourite but much cheaper, and it has more nutrients
like calcium, iron, potassium, manganese, magnesium, etc.

The benefit of either the Flourite or the Profile is that they provide
iron and other minerals for your plants' roots, but it doesn't get up
into the water column. They don't really need to be amended except
for really heavy feeders, IME. They're rounded enough that they're
safe for loaches and catfish. They're also very attractive.

Flourite: http://www.thatpetplace.com/images/p6130b.jpg

Profile: http://www.metrocast.net/~randall/chirotank.jpg
(in a newly-planted tank I set up for my chiropractor)

You can see a chemical breakdown of a lot of different substrates at
this page: http://home.infinet.net/teban/jamie.htm

See ya,

Kristen