Well, Sugar, just to make you happy I will poke it later today, I am going to be moving some rock from that tank to another in preparation to rearranging the whole mess, so, I will give it a poke.
no bubbles, no freaky creatures from the black lagoon, no tunnel looking things, no clumps of deitirus, in fact it looked like perfectly clean sand.
Then, about 20 minutes later I was sitting on the couch and out of the corner of my eye I saw a chalk bass come out of a hole, turn vertical and take a mouthful of sand from the bottom and then drop it.
Apparently, its the fish....
weird huh?
after this week it should stop completely, because I am rearranging my tank so I have better flow.
Before you slap the cuffs on the fish, you might want to try one more thing...
I had/have the same thing happening daily in my tank. All these sand piles kept popping up on my sand bed and would reappear after stirring it w/ a fish net... Took a turkey baster and blew at the sand w/ it gently and lo and behold there are all these sand tubes sticking up vertically throughout my sand bed. I've since watched them and they are some sort of worm that seems real similar to the tube worms that appear on the rock. Extremely clear, can stretch quite a ways and usually two sticking out of each hole. They seem to get the sand stuck to them as they're searching out food on the sand bed and somehow get the sand off before retracting into their tube. In the process continually building their tube...
Just another possibility for ya, might also explain what the fish was picking at...
I have those tube worm things all throughout my sandbed. I discovered them when a powerhead fell off the side (damn suction cups) and blew a nice trench in my sand bed.