[AGA-Member] Substrate Critter?

["Miles Morrissey" <sheamorrissey@charter.net>]

I've been enjoying planted tanks for about 10 years and have settled on Jim Kelley's loam and vermiculite substrate with good results.  I currently have 4 tanks set up with this system, one of which has been evolving for over 8 years.  I've used two types of snails in these tanks, (can't remember names) the red ones that don't grow more than an inch or so and the cone shaped ones (malaysian trumpet snails?) that burrow through the substrate to help with aeration.  I have both of these snails in all of my set ups with out incident.  SOooo I am stumped by a problem I'm having with the 47g tank I have in my office (of course the most public tank I have)  It was set up last February and has evolved nicely for the last 10 months with 4 Angels 4 Otto cats and 2 Siamese Algae eaters.  About 2 - 3 weeks ago I noticed mounds of silt and vermiculite appearing on top of the gravel.  This gravel is the same river gravel and sand blasting grit I use in all of my set ups.  The gravel and loam substrate were baked thrououghly prior to set up.  The aforementioned mounds have increased in number of course leaching nutrients into the water not to mention clouding it with the slightest distrubance.  I began to have algae problems that I have not experienced prior to the mounds appearance.  Any idea what critter is causing this?  This is my office tank, I'm positive I have added nothing to it lately so I imagine what ever is doing this has somehow come out of dormancy or maybe I have a mutant cone snail or something.  These are big mounds measuring several inches across.  It would seem that the critter would need to have some size.  I have not seen anything that I have not already identified.  Any ideas?  

Thanks,  Miles Morrissey   Easthampton, Mass
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