Some threads never die

     On page 48 of the 1983 edition of Exotic Tropical Fishes, Herbert 
     Axelrod wrote:
     "European aquarists sometimes use peat, loam or earth beneath the 
     gravel or in pockets of rock to  nourish the plants.  General 
     experience is, however, that such materials sooner or later cause 
     trouble; either they get stirred up and make a mess of the water or 
     they turn bad and have to be removed.  If one is interested primarily 
     in growing fine plants it is possible to take care and use these 
     substances, but they are hardly to be recommended for the amateur.  
     The plant growth that results is from the material supplied beneath 
     the gravel, and the plants may not, therefore, be performing their 
     essential function of removing much of the waste products of the 
     fishes as well as they otherwise would.  This is a point which hasn't 
     been clarified, and further research and observation are needed."
     This discussion sounds vaguely familiar...