[karimwassef]

Randy's theory of the dinos being dependent on some other element may be relevant here. An excess of something that we're not used to measuring could excite them. It doesn't have to be a nutrient or a toxin. It could just be a non-reactive or trace element that dinos depend on and that are not common in most tanks. Maybe a little pollution gives them a boost. Maybe it's a pesticide or air spray that was accidentally introduced...

I guess a test would be a complete transplant of life from one system to a completely different new system (different equipment, etc...) to see if the dinos travel with the rocks and sand or if they disappear due to the absence of another source of pollution.

If they disappear - then it's a pollutant in the equipment/system.
If they reappear - then they're traveling with the rocks and life.

I personally don't think it's the result of a thinwall rubbermaid container since I don't use any. I do use the thick agricultural grade stuff.

If would be great to isolate a chemical source though.