White sand turning black

[Scottw68TN]

My sand is turning black! In a QT tank (5.5gallons) has had little attention with a corner filter could this be an algae? trying to house my new mollie fry but think I should start with a 10 gal new sand and scrap the corner filter for a penguin mini.

 

[Scottw68TN]

anaerobic?

 

[Scottw68TN]

Anaerobic sand can lead to all sorts of problems - from acting as a “disease haven” to releasing highly toxic chemicals such as hydrogen sulfide So Being the paranoid I am I chucked it all got some new stuff. I was going to get some black sand but now don't want it due to not being able to see the reaction.
Found this to support my fear:

When the sand is live there actually are no true anaerobic bacteria, but bacteria that live in an anoxic area (very low in oxyen). They are callled facultatively aerobic anaerobic bacteria. If the oxygen levels falls too low they turn anaerobic and you get hydrogen sulfide, if the oxygen stays real low but sufficient they feed on NO3 and on O2 and do not go anaerobic so no hydrogen sulfide is produced at all because there is no anaerobic decomposition taking place.

To achieve the anoxic level and not the anaerobic level you need the stand stirrers. Another very very important point that is not frequently mentioned is that the higher the oxygen content of the water is, the less chance of H2S and anaerobic activity because O2 diffuses into the sand to a very small degree

 

[Allivymar]

I have sand in my 10g tank, in levels from 1 1/2" to 4". But, I have plants with quick growing roots (oi, they are takin over the tank!) which keep the sand aerated. Hydrogen Sulfide is REALLY dangerous.

I do kinda think it was algae tho in your case; at least the stuff on the top. Dunno if there were also anaerobic bacteria in there. I'm guessing you never stirred the sand/didn't have snails or sand burrowers/plants in that tank?

Also, ever think of writing an article about it? You've got a great start right there.

 

[Scottw68TN]

Had 40 mts snails in there and stirred it 2 weeks ago.