smelly substrate?!

so i got a new tank 20 gal tank to upgrade my two scorps 10 gal. give them more to dig, and maybe add a new roommate or two. i set the gravel for the false bottom and was going to use the substrate i already had in the 10 gal to help fill the larger one... well as soon as i started digging into the coco fiber it smelt HORRID. I was suddenly hit by a powerful rotting egg smell. Not sure what it was or if it was normal. im keeping them out of it just to be sure and going to buy more substrate in the morning.
has anyone encountered anything like this? I did not see any mold in the substrate so its a mystery to me.
I just want to know if i should be on the look out for anything...
the tank setup is a 10 gal with 3 inches of gravel for a false bottom. 4-5 inches of substrate. and i have it a constant 86 degrees F. and i have an acrylic top with just small holes for ventilation to keep the humidity up.
I'm thinking that having the lid might be overkill and not letting any moisture escape. there is a lot of condensation build up on the sides and ceiling of the tank.

Anaerobic bacteria. I haven't had it my scorp tanks yet, but I have with my hermit crabs (and a fish tank once) before. It's usually caused by the substrate being over-saturated, which causes a lack of oxygen in the lower regions and allows for the growth of the funky sulfur smelling bacteria. It can be harmful as it is toxic, so it's great you found it.

Maybe mix up the next batch of substrate to be a bit dryer to start, and keep an eye on the moisture levels? It's always so hard finding the right mix of just enough moisture for tunneling but not too dry or too wet to cause problems!

thanks for the info i was completely caught off guard... toxic huh... soooo me getting a few good wiffs of that should i be worried? haha
well they had a deep tunnel going on before i moved them. i thought they just dug one small hole they shared but i actually had to dig em out. i was pretty impressed.
for this next tank im going to go with the screen top and let more airflow and just see how the false bottom works out with keeping the moisture. hopefully i can avoid a repeat of this. i think it was i over did the humidity.
my analog humid gauge sucked, and its broke now so i kinda went for "ill just make it as humid as possible" option

Hi Vic,

I'm curious what brand(if any) did the substrate came from?

I'm using Exo-terra coco-fibre bricks and i do notice a strong pungent smell each time i moist a brick into a big bucket of loose substrate. Although the smell is strong (e.g. can easily spread in my living hall) but not really to the point of "rotten eggs" odor..

Weird that you would get that from the Exoterra peat. I buy my peat bricks from plant nurseries and I have never had the problem of it smelling bad. I even keep some of the left over peat VERY wet so that I can use it later for new arrivals and such.

Not that bad actually, it just has this strong scent of "fresh soil" (lousy example i know) kind of pungent scent but still bearable

I use eco earth coco fiber, i never noticed a smell first using it. not even a fresh soil smell. Im leaving now to go buy replacement substrate now.