[Cannonbolt]

I once heard that moving around something like a large piece of wood buried in the substrate could release pockets of gas that could poison the fish. Is there any truth to this? I don't think I'll ever be able to catch my fish unless I move this big piece of wood.

 

[l8nite]

It happens occasionally, but I wouldn't worry too much about it. It will just smell like a bad fart for a bit.

 

[wkndracer]

There is truth to large substrate areas being sealed off by blocking gas exchange with larger scape pieces and allowing gas build up, that's true enough but reports of massive kills disturbing things is very rare. The bubbles rise very quickly with little surface area so the release is mostly to atmosphere.

That said you don't want to turn over all your substrate at once :icon_eek:

 

[zoragen]

If you are worried - maybe poke (with a pencil or something) the substrate around the DW a few times.

That might release any gas a bit at a time?

 

[DogFish]

Not so much a myth, more something blown out of proportion that creates undue emotional stress.

As wkndracer pointed out gas exchange is an important mechanism.

It's easy to avoid by either having hardscape elements lie directly on the bottom glass of the tank Or, prop them on sand bags or base rocks that are on the bottom glass.

I also pick pc of heavy wood like Mopane that have small contact points where they sit on the surface of the substrate. This way plant roots can grow under them easily.

The activity of MTS(snails) is enough to facilitate gas exchange in sand cap plantings so that poking around with chop sticks and pencils isn't really needed.

 

[rainbuilder]

I have tons of gas bubble up from my substrate every once in a while, like when I replant or do something with the substrate. It does absolutely nothing to the fish and I have a hard time believing that the gasses could be bad for them. There is barely any time for it to dissolve into the water, and like posted above, the only way I see it being harmful if it was trapped in very large quantities for longer periods of time.