I've had my NPT set up for coming on three months now. Was told I wouldn't need to poke at the soil as it's capped with very fine gravel. I was siphoning out some snail poo in some hard to reach places with a turkey baster when I bumped the gravel a little roughly and some large bubbles came out. There was a smell of sulpher, not overpowering but there. Plants are all healthy. Betta and snails seem fine. Ammonia, nitrite, and nitrate are all at 0.
So what should I do? Poke until all the bubbles come out? Remove fish and snails before doing so?
Is the only cause of smelly bubbles substrate going bad? I've heard npts can bubble for the first few months as everything settles. Could it merely be bubbles that were trapped under the substrate and smell like sulphur from whatever is in the dirt? It's miracle gro organic potting soil if that helps.