Serious Anaerobic Bacterial Build-up In Sand, With Smelly Water

[wodesorel]

My filter got plugged up overnight or I wouldn't have even noticed it, but when I went to clear it the entire tank smelled like the mixture of sulfur and methane. Looking at where the sand is above the bottom rim I can see dark grey/green patches growing. I had a massive snail die off about a month ago and I never even thought about what that meant for the aeration of the sand bed. I'm also not sure how to fix it now since it is so severe. Since the water has started running again the smell has completely disappeared, and all the fish have been acting normal.

I do have a spare tank I can set up in an emergency, but it's a used tank and I wasn't planning on putting fish in it since I don't know it's history. (Bought from a charity sale.) I'm afraid of what might have been in or used on the tank so I do want to avoid having to move the fish unless I absolutely have to.

The affected tank is a 20 gallon tropical freshwater with a betta, 7 kuhli loaches and 2 clown pleco. (I've had several of the kuhlis since 2004 so they are very special to me.) Substrate is CaribSea fine grain white sand (4 years old) and Exoterra Turtle Pebbles (2 years old). I tore the apart completely and cleaned everything (including boiling the sand) 2 and half years ago. Up until a month ago the sand bed had been taken care of by an army of MTS.

What I'm hoping to avoid is having to tear it down completely, but if that's what has to be done then I'll do it. Ideas or advice??

 

[Aquascaper]

Just run your fingers gently through the sand or use a plant stick to break up the compacted sand, the anaerobic areas will quickly dissipate.

 

[WILDER]

Do you mean your filter got unplugged?
Just make sure the algae does not look blue in colour.
Sulfur smell can mean bad bacteria running rampant in your tank. So
I would carry on with sand vacs, removing ornaments, wood, etc. Water changes.,
Did you remove the dead snails. As they can become toxic to fish when they start rotting away.

 

[BerryAttack]

off with sand.. one day i was cleaning gravel and wanted to see if it would with sand... but since sand is so much lighter i know that i wouldn't be able to do it in that way.. but you can use it to skin the top of the sand really fast.. and the go deeper into the sand.. before it sucks it up... might be easy to do and then the stuff isn't floating in the water.

 

[wodesorel]

Great! Thanks. I'll start off with a heavy water change today and then work my way through loosening up the sand and making sure it's mixed well. Should I be afraid of doing too much too quickly? Would it be better to do a third of the sand bed today and then do another water change tomorrow and another third of the tank? I know how dangerous hydrogen sulfide can be, but I don't know how much can be created in a 1/2 inch (1.25 cm) of sand.

The filter actually got plugged up and lost suction. It's been a while since I tore it down and cleaned the pipes with a toothbrush, and the clown pleco poop mixed with some minor algae causes slimy sludge buildup. I waited a little too long this time.


I did remove the snails as they died. Not sure what happened, but I did a water change about a month ago on all my freshwater tanks on the same day (4 other tanks, all smaller than this one) and every single snail died. 2 nerites, a bunch of ramshorns, and all the MTS. I have a few spikey-tailed ones that survived and that's it. This has happened before, about once a year, and I think it's something random in the tap water. A few of my fish aren't doing well either at the moment (not in this tank, and all three in separate tanks), but that could be from other reasons. Water parameters have always been 0ppm ammonia, 0ppm nitrite, 5ppm nitrate, 7.2 pH on every tank.

So far the drift wood and fake plants look and smell okay. It's just the bottom of the sand I think that's affected.

The sand is so old and has been cleaned with a gravel vac so many times I can almost treat it like gravel as the only grains left are heavy and won't fly all over. I"m hoping I can do a modified deep gravel clean on it without loosing too much. (And even if I do, I can always drain off the old water and save the sand that's in the bucket and boil it before putting it back in.)

 

[WILDER]

Maybe do half of the sand tonight. The rest tomorrow.