Hydrogen sulfide?

[TriggerFinger]

My sand was 2” when I set up the tank. Recently, there is a corner in my tank that has an ever growing sand pile. I don’t know if spaghetti worms are pulling the sand in or the flow is blowing it. I also noticed there are dark areas in this corner. Is this algae growth or hydrogen sulfide forming? Can I smooth out this corner of sand? I’m wanting to move that rock back towards the corner and don’t want to have a disaster if it’s not just algae growing. Any thoughts?

 

[dwest]

I would think H2S would be more black. I’d say it’s algae. I also don’t think the worms would be there if it were anoxic. I think it’s ok to smooth out if you want. If you get a big whiff of rotten egg small, then stop.