This might be dumb...

[RobertA]

I just notice that under a part of my driftwood there's a big bubble of air. I've heard that before spawning, fish make bubbles to start the spawning process. Do you think this might be a fish nest? Or is it just some trapped air...? :huh:

[indiginess]

if its actually on the wood, and the wood is fairly new, i'd say its air. many of the bubble nesters build on top of or beneath fine plants.

depending on the piece of wood, they can take a very long time to completely release the gas (saturate).

[liv2padl]

is it just some trapped air...? i thknk it's safe to say YES. labyrinth fishes such as betta and gourami make "bubble" nests for egg disposition but these are almost always associated with the surface of the water and are in fact fine "bubbles" ... never one large air bubble.