Bubbling Sand (and there's no airpump)

aeroflight · Post by **aeroflight** » 26 Jun 2003, 04:11

I just noticed that the sand substrate on one side of my tank was releasing bubbles of gas every now and then. I knew this could be trouble, so I went over and stirred up the sand like I do every week when I do my water changes (just did one last Sunday). Up came the bubbles like a carbonated beverage, only I wouldn't want to drink the water. I could definitely smell sulfur. This can't be good, right? What do I do? What's causing these bubbles? I've always been good about stirring up the sand to supposedly avoid problems like this.

Here's some more details ...
I've got a 135g tank with a pool filter sand substrate that's about 1.5" deep. It's usually a nice light tan color, but I've noticed that the sand around my driftwood has turned a dark grey. I thought it was just basically sawdust from the sailfin pleco nawing on the wood. The sand that's producing these bubbles is the darkest part, too. Maybe there's a connection? Any help would be great.

None of the fish are acting distressed, but I'd like to get this figured out before I leave for the weekend ...

Post by **Silurus** » 27 Jun 2003, 00:51

Your sand is too fine and is trapping areas where there is no oxygen. This is causing anaerobic bacteria to thrive and the smell you are getting is the hydrogen sulfide they are releasing as a result of their metabolism.
You can either use less sand, or use coarser sand. Don't stir up the sand. Hydrogen sulfide is toxic to the fish.

Post by **Barbie** » 27 Jun 2003, 02:24

I definitely agree with HH on this one. I had this happen in a tank full of shell dwellers that insisted on piling the sand up as dividers between territories. I did eventually have to remove most of the sand from the tank. Any time they got the depth to more than an inch there would be black smelly film on the bottom of the tank that I could see when I looked up from under the stand. I know of a couple instances of people losing tanks of fish due to those anaerobic pockets. If you decrease the sand depth and add malaysian trumpet snails (burrowers) it usually takes care of the problem in my experience.

Barbie

Post by **Dinyar** » 27 Jun 2003, 04:08

Malaysian Trumpet Snails

I love animals, and know many people swear by MTS, but I think of them as the cockroaches in my fish tanks!

S. Allen · Post by **S. Allen** » 27 Jun 2003, 05:22

never had a real problem with my sand, and it's probably an inch and a half or more... but the stingrays keep it turned over well enough.

aeroflight · Post by **aeroflight** » 27 Jun 2003, 18:49

Thanks for the help. Any ideas as to whether the sand's change in color (from tan to grey) is due to the driftwood (essentially sawdust particles in the sand) or the anaerobic bacteria?

S. Allen · Post by **S. Allen** » 30 Jun 2003, 01:49

could be both... sawdust particles are biological material, could get mixed in and decay like waste and food. another possibility, more likely I'm guessing, is that if it is directly under the driftwood... that tends to be the area of sand that gets the least circulation, becomes more compacted, as well as being the area of sand that gets disturbed by fish, tubes, currents and stuff least, making it an ideal location for the aneorobic bacteria.

aeroflight · Post by **aeroflight** » 30 Jun 2003, 15:20

I came to the conclusion that the sand changed color due to the anaerobic bacteria. Before I went away for the weekend, I moved all of the rocks and driftwood over to one side of the tank (creating a lot more hiding spaces) and left the more anaerobic side clear. When I returned home late last night, the once dark grey sand on the "bare" side had returned to its normal color. The deeper sand still had the dark color. I'm guessing that without the driftwood covering the sand, the anaerobic bacteria died off and the sand's color returned.

I'm planning on removing some of the sand and having a shallow-er substrate and considering putting in a powerhead or something to get more circulation. I'm not too worried about blowing the sand around as I'm using 20 grit sand, which settles quite rapidly.

Post by **Silurus** » 30 Jun 2003, 15:28

Yeah, I had that happen to me as well. That dark gray stuff stank up my office for a week after I had torn the tank down.