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Just so that I can expand my knowledge, can anyone tell me what anaerobic gas is, how it is produced, how to get rid of it and how to prevent it.

TIA

Robbie

Anaerobic gas is the gas that anaerobic bacteria produces. Anaerobic bacteria lives in your gravel or sand, where there is no water movement. Oxygen kills it. You can prevent it by stirring your substrate.

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They shade the glow of it with their mossy-misty costumes,
They wear masks of silk, porcelain, brass, and silver,
So as not to mislead with their own, ordinary faces.

The gas comes from when there are packets in your sand (the chance of it happening in gravel is kinda rare) and when a fish digs it up, it realeases the gas (that dissolves) into the water, and is harmfull to your fish.

It will occur anywhere there is no flow, not just in sand. It can occur under hollow decorations, for example. Many fake decorations at the LFS are hollow and shouldn't be used for this reason. Sadly, it was my mistake for putting one in my tank that killed off one of my fish because of the gasses that had developed inside.

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The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.

I've noticed a lot of larger decorations - those intended for cave space as well as decoration - have holes on the top as well as the bottom, so I'd imagine this isn't such a problem with them.

I've heard of it happening with slate-held driftwood too. If the slate has any gravel under it, it's extremely anoxic and a good old hydrogen sulfide bubble forms right there. Pick up the driftwood, and *boom* suddenly you've got two dead fish and a water change you didn't want to do. ]:|

Oh, one other thing. According to my plant book, plant roots emit oxygen, so the area around the roots of a plant tends to become oxygenated. A heavily planted tank with four inches of gravel and plants on every square inch isn't in nearly as much danger as an unplanted tank with those same four inches of gravel.

Are you sure about that? I'm 100% sure that roots do NOT emit oxygen; they don't photosynthesize in the least, only respirate. Thus, they would use oxygen and release carbon dioxide.

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The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.

My source is Peter Hiscock, "Encyclopedia of Aquatic Plants", pages 45-47. A quote from the main text:

"In a well-planted aquarium, the majority of organic debris will be broken down by bacteria and the resulting nutrients are taken up by plant roots, which in return release small amounts of oxygen into the substrate and help to prevent stagnation.... However, a buildup of organic debris in the uppermost layer may not be broken down very quickly and plant roots are not present in sufficient quantities in this area to keep the substrate oxygenated. Regular gentle stirring or siphoning of the top layer will...keep the substrate clean and healthy."

I'm not willing to make a personal guarantee that roots emit oxygen, I'm just citing an expert who says so.