Dark Spots in Sand

[carfac]

Hi:

First, thanks to everyone who has been so helpful here, either diretly by answering my questions, or indirectly by posting and answering other questions. I have learned a LOT here!

Now my sand, where it meets the glass, is showing dark spots from 1/4 to 1/2 inches down. These look like little caves or something. Very small, about 2 to 3 times the size of my sand size. I seem to remember reading somewhere this is things in my sand doing their thing, but I wanted to check. What is doing this?

I am very happy, things seem to be running just great. I have corals (Zoos, mainly) showing up, anipods, dusters, all kinds of good things. And I heard this was a difficult hobby! :D

Oh, another question: I went to a new LPS today, and he sold me someting he swears by. It is a photoplankton soup that you add an ounce or so of a day. It is a quart jar of green liquid, keep it in the fridge. Is this a good thing, or was I fed a line?

Dave

[bertoni]

The dark spots are likely anoxic regions, and the dark areas are showing the effects of hydrogen sulfide. That's normal.

The phytoplankton product is probably a good idea, IMO. Either DT's or Phyto-Feast should be good foods. Either will feed an array of animals in your tank.