Bubbles coming from the substrate
I have a tank with substrate from garden topsoil. It has been there for over a month now, has plants, and the tank inhabitants are Chinese fire-bellied newts.
Today, I noticed that some areas of the substrate are starting to rise. When I put my hand on the raised area, bubbles came out of it and this stirred up the soil.
The newts are in there, though they have ran to the other side of the 36" tank, away from the "eruption".
Would this be harmless to my newts? I did a water change just to be sure, after I pushed the soft substrate areas down thus releasing more bubbles.