Sorry for the lack of details in my first post. We had a 20 gallon tank given to us the first week of July, and decided that we wanted it set up differently than it was. The tank was originally set up with crushed coral substrate, but we wanted to convert it over to sand and live rock. My husband felt that since the coral had already been in the tank for well over a year, that we should leave most of it because it probably contained the algae and bacteria that would help our sand out. We made a sandbed in the tank that is approximately 3-4" deep, and added 3 pounds of live rock. We also added rock that I scrubbed in vinegar water and then boiled to ensure that nothing was living on it that could harm anything in the tank.
All tests to our water have turned out fine. Salinity is at 1.024. But in the past week we have noticed a black growth starting in our sand bed, and it seems to be "confined" to the right hand side of our tank. I will enclose some photos of it. It is my fear that either leaving the crushed coral, or adding the extra rock has done this. (goes to show that a newbie like me really needs to just go by what the experts say
)
Our worry now is that if whatever this is, isn't good (which I fear) that if we disturb the sandbed, we'll unleash a host of other problems too. Help!!
*forgot to add: we have an aquaclear filter pump and a bubbler placed on the back of the tank glass to improve circulation without disturbing the sandbed.
