Anaerobic substrate- what happens?

[|squee|]

What happens when you have a anaerobic substrate? I remember reading about it when I was in the early stages of this hobby. Can anyone list out what you'll get when your substrate goes anaerobic?

[PeterGwee]

Poor plant growth in that particular area. Deep vac the substrate yearly as well as routine uprooting of plants instead of topping the plants will prevent such issues.

Regards
Peter Gwee

[vinz]

- Light coloured substrates turn black... but you won't see it unless you dig.
- Poking around the area will release a foul smelling gas (which I forget), often described to smell like rotten eggs.

Possible remedy without changing the substrate: plant Sagittarius subulata in the area. It'll take some weeks/months, but their roots will penetrate the area and oxygenate and revive it. It's a tough enough plant to still survive well.

[Justikanz]

Anaerobic substrates will create pockets of hydrogen sulphide, which can be released... Not sure if it is not good for the fish but it smells like rotten eggs... What else? Hmm...

[bclee]

Yes the foul smelling gas is hydrogen sulfide (H2S). H2S is the product of anaerobic bacteria that reduces sulfate to H2S or digest organic matter. H2S is toxic to fishes.

Roots of heathly plants will help to aerate the substrate to prevent it to go foul. But once the substrate has gone foul, you will have poor plant growth in that area. Like Peter mentioned, it can be alleviated by vacuuming the substrate... or you can try planting some fast-growing, deep-rooting plants like Sagittaria sp. in that area to help to re-araete the substrate.

BC

[|squee|]

Thanks very much for the replies! I asked this question because I feel that it's time to change my 2 year old Aquasoil substrate... I see bubbles on the oil layer in the mornings and whenever I touch the top layer of the substrate bubbles pop out.

[vinz]

Those bubbles from the substrate could be oxygen bubbles. Which means your plant roots are healthy and providing oxygen to the bacteria in the substrate.

[Justikanz]

Actually, it is also possible for nitrogen gas to be produced in substrates... Smell the gas from the water surface (Not too near! Dun wanna to faint eh in case it turns out to be H2S!... )...

[valice]

errr thomas...
nitrogen got smell one meh?

but on the serious note, how will we know whether those bubbles are oxygen or nitrogen? i see some bubbles in my substrate now...

[vinz]

Oxygen is a good sign.
Nitrogen is ok.

We don't need to detect them and besides they are odourless.

Hydrogen sulfide is not ok.

Fortunately, it has a really foul smell. Disturb the suspected area of substrate and when the bubbles float up and burst at the surface, take a whiff... if it smells bad, your substrate is bad.

[Justikanz]

errr thomas...
nitrogen got smell one meh?

but on the serious note, how will we know whether those bubbles are oxygen or nitrogen? i see some bubbles in my substrate now...

Haha... I was refering to the H2S... That's why I asked him to avoid standing too near, in case he took a deep sniff!...

I posted that before Vinz and so did not get to read Vinz's post...

Oh, add on... Actually, an aerobic substrate would smell fresh and the gas emitted should carry a faint fresh smell...