Observation of dismantling a deep sand bed.

[vlangel]

Last night I took down my reef tank to move my seahorses into my 36g bowfront tank. It had a DSB that I put in Dec 2012, making it almost 3 years old. Seahorses need at least 19" of height for their courtship dance so the sandbed had to become a shallow sandbed. As I was removing the sand I first of all noticed that it smelled like fresh ocean water and not rotten eggs. Many folks are afraid of DSB because of the gases given of by the anaerobic bacteria but I have never experienced a problem from one and I like the 'no maintenance' of them. Of course the denitrifying aspect is nice as well as for controlling nitrates. The 2nd and most interesting thing I noticed was that at the very bottom the sand was a different color. It was a dark tan color instead of off white. It was never more than a quarter of an inch thick. I wonder if that is where the anaerobic bacteria lived? Has anyone else ever noticed this?

[ajmckay]

Interesting observations - thanks for sharing. Any other information such as the depth, type of sand, etc?

[Murphs_Reef]

Following this

[vlangel]

The sand was just Home Depot play sand with sugar size oolite on top. It was originally put in my 90g reef in 2004. I can't believe I did this but when I downsized to the 36g bowfront in Dec. 2012 I used the same sand. Again it smelled like fresh ocean water, not fishy or sulfurous. I did assume at that time that most of the denitrifying bacteria would have died in the transfer. The bowfront barely went through any cycle though so I am not sure. I made it 5" deep and it never got disturbed below the top 1/2".

[spinycheek]

That is interesting. Could have been a low bio load in the sand, so there wasn't a lot of stuff to break down in the first place. Or maybe you have some magic strain of bacteria that doesn't make hydrogen sulfide.

[vlangel]

That is interesting. Could have been a low bio load in the sand, so there wasn't a lot of stuff to break down in the first place. Or maybe you have some magic strain of bacteria that doesn't make hydrogen sulfide.

I don't know either and it is interesting. In the 90g I generally had 11-13 fish which is not a light bio load. When I downsized to the 36g I kept 7 fish which is a lot for that tank too. I am careful not to over feed so that helps not to gunk up a sand bed. Anyway, it was neat to see the good condition the sand bed was in.