Sulfur Gas in substrate?

[Marnol D]

Hello,

I was doing a water change today and noticed as I was gravel vaccing that the water coming out smelled of sulfur. So me being the "ill just see what happens" type of person I am I grabbed my planting tweezers and started running them through the substrate (4 inches of gravel) and sure enough bubbles would rocket to the surface and release a sulfur smell. Now I don't know if this was the correct thing that I should've done  ,but I thought it would be safe to do  as I was doing a larger water change than normal (knocked some food into the tank the rest you can probably guess what occurred). So will the fish be fine or should I go ahead and do another water change this afternoon? (the water doesn't smell of sulfur now)

I usually gravel vacc but I skim the surface rather than deep dive into the substrate where I don't disturb the root tabs or root systems of my plants. Do I need to keep watching out for gas build ups in the substrate? What is the gas building up technically? Should I keep doing deep gravel vaccs to release the gas or just make sure I turn the substrate every so often?

 

 

[Daniel]

It is very likely hydrogen sulfide. It is a product from the metabolism of anaerobic bacteria in the low oxygen part of your substrate. Some people are concerned about it, but I doubt you will ever experience it at levels that could be harmful to your fish.

[Marnol D]

@Daniel

Thank you! Now that it has a name I can fight it. Do you think I should remove some of the substrate to make it not as thick? (only reason its that thick is I managed to get a ton of gravel for $1 so I added it all to the tank and it makes planting rooted plants easier) Il add in another airstone and turn of my CO2 to see if i can gas it out and ill leave the top off the aquarium so it doesnt sit on the surface.)

[Daniel]

Not sure. I agree the 4" depth is what allows the oxygen free zone, but disturbing might be worse than just leaving it alone. I would be interested to hear what other people on this forum experiences were. In the past I have had deep substrate like you have and it never caused any trouble, but I also never tried to gravel vac it.

[Marnol D]

@Daniel

Ill probably still only gravel vac areas without plants. I may start turning the substrate every so often as to make sure no gas is building up and that  mulm and waste are being "tilled" into the substrate for plant roots to get at. Since I already disturbed the substrate and I think i've released all the gas (while still siphoning the tank) 

[Brandy]

I'm going to get science-y. According to Wikipedia, humans can detect H2S at 0.047 parts per billion, and toxicity is far above that level. Even in deep aquifers where H2S can be dissolved in the water over a long time (due to not being able to escape to the air) one of the common ways to remove it from water (for drinking) is simple aeration. I think you are right on the money with your air stone, and even if you never disturbed the substrate, the aeration would more than solve the problem.

Edited December 14, 2020 by Brandy
I can't type

[Irene]

I agree with what @Brandy and @Daniel said. I have about 2-3 inches of Eco-Complete in my 20G planted tank, and I occasionally see a random large bubble escape from the substrate when I'm not even doing tank maintenance. I have a sponge filter and the H2S gas doesn't seem to ever occur at high enough levels to affect my fish, so I've never been worried about it.

[Coronal Mass Ejection Carl]

http://www.history.com//favicon.ico Gas cloud kills Cameroon villagers - HISTORY

WWW.HISTORY.COM

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An eruption of lethal gas from Lake Nyos in Cameroon kills nearly 2,000 people and wipes out four villages on August 21, 1986. Carbon dioxide, though ubiquitous

 

[H.K.Luterman]

I call these aquarium farts. 

 

[AdamTill]

I never worry about it. I’ve watched cories swim right through a big gas bubble and not even flinch. I had a tank for over a year that was up to 9” of peat in places, and it would burp frequently. No issues. 
 

Think how many bubbles a sponge filter needs to create to be useful, and how much transfer you get with only one or so.

I will say make sure not to have burpy substrate with large plates of foam etc that are tenuously anchored. I heard once of an aquascape that went full versuvius when such a thing erupted due to gas buildup. 

Edited December 16, 2020 by AdamTill