My Cichla is digging the exact same way: put gravel in his mouth and release it to the side. This is the first time I saw em do it and he is still doing it as I type so I did a search and found this thread. My Cichla is only about 6" or 7" only and he is the only Cichla in the tank. He's doing it behind a big rock so I assime he is picking out a place to nap tonight. I guess I will find out for sure tonight but does anyone know what he/she is up to?