Hydrogen sulfide gas bubbles?

[rodger]

I have an overstocked, heavily fed, yet way overfiltered 240. Filtration is a 100 gal sump MB filter with 100 L of K1 and a Eheim 2262 with about 18 L of Seachem Matrix. I have a gravel substrate, about 3" deep and do weekly 1/3 to 1/2 water changes. I vacuum the gravel weekly as well, which is why this is puzzeling. Over pretty much the entire gravel bed I have a lot of gas bubbles that travel up the tube of my python. I hit the entire floor of the tank EVERY week. I thought that H2S was a sign of anaerobic activity but I don't see how that is likely with my filtration and maintenance. I have no fish health issues from it, as the gas mostly goes out with the waste water. Do you who know more than me think this is H2S or another gas? Has anyone else observed this? I have no fish in this tank that stir the substrate.

 

[xraycer]

Perhaps there are anaerobic activities inside the gravel granule itself

 

[Burbotman]

Gravel is very efficient at trapping detris, 3 inches of gravel could be the issue. Doesn't sound like you are having any issues. Unsettling though

 

[12 Volt Man]

its not anaerobic pockets as you would smell the H2S pretty quickly and the substrate detritus would be black coming up.

I have seen this before and its likely one of two things:

1. microbubbles from when you fill with your python get trapped in the gravel bed and aggregate together. so when you python the next week they come out as larger bubbles.

2. in planted tanks, some dissolved O2 can be released via the roots and form bubbles in the gravel. again, you python them out.

I quite often get case 2 with my 65 planted full of vallisneria

 

[rodger]

I don't have a planted tank. I don't believe it is bubbles after filling. I fill it on an end of the tank and the bubbles come from the entire 7' of the tank. There is no smell to it. Anyone else have an idea?

 

[Drstrangelove]

Well, the smell is really pungent, so have a second person with you next time, stir up the gravel and let them take a whiff. No smell means no problem. If you still worry, or if that is the issue, reduce your substrate down to 2 inches and it will eliminate the problem.