Tank has sulfur smell

[BarbaraME]

Hello. I have a 15 gallon Fluval Flex. I have had it up and running well since December. I do the regular maintenance and weekly water changes. Everything has been going well up until this past Sunday. I have live plants, mountain minnows and nirite snails.
On Sunday when I was doing my water change I replanted one of the plants in the gravel. This disturbed the debris underneath. On Monday I woke up to find 2 of my fish dead and the others all gasping at the top, even 4 of my snails were at the top. I tested the water and discovered that the nitrite levels were in the high stress zone. I performed an almost 50% water change, this brought it down some, but the fish were still struggling.
I did a complete break down of the tank after moving the fish and snails to a different tank. The gravel was extremely dirty, which was not a surprise. I got the tank back up and running, ran for 24 hours. Tested both tanks and the parameters were the same so moved every one back to their tank. Not sure what happened, 5 of my 7 remaining fish went belly up suddenly and the tank has a sulfur smell.
There is a bacterial bloom, which I had expected. What is causing the smell as I cleaned everything?
Is it the bacterial bloom and will it go away with that?
Will my last two fish survive? Any advice would be appreciated. Thank you.

 

[Aiken Drum]

Sulphur smell is sulphur dioxide, usually caused by decomposing matter causing pockets of gas in the substrate which get released when you disturb the substrate.

Can also be caused by nitrifying bacteria growth in deep substrate where oxygen starved bacteria can grow which process nitrate into nitrogen gas and sulphur dioxide.

Not sure how you can have this sulphur smell if you broke everything down. I presume this includes washing the substrate.

 

[BarbaraME]

Yes, I did clean the substract/gravel well. The bacterial bloom has subsided and the sulfur smell has started going away, so maybe it was being caused by the bacterial bloom? Could it be coming from the foam block even though I rinsed that too?

If two tanks have the same parameters and the temperatures are the same, should you acclimate the fish when moving from one tank to another? I am trying to figure out what caused most of my fish to suddenly die when I moved them back into their original tank when they were all fine in the temporary tank and everything matched between the two tanks. Anyone else ever had thus happen? Thanks, Barbara

 

[Aiken Drum]

I move fish between tanks quite regularly without incident. Remember there are numerous water parameters you probably arent testing for though. What did you test for?

If we are saying all your fish died pretty quickly after they were introduced and the common things you test for matched up, then it could be insufficient water conditioner, or maybe some detergent in the water. How did you clean the tank?

If it was overnight, in addition to the above things it could be a difference in disolved solids which wouldnt show up from a standard testing suite. Or maybe a lack of O2. Moving fish about is always stressful. Maybe just the high nitrite they were exposed to and then the stress of being moved repeatedly.

 

[BarbaraME]

What did you test for?
First I used test strips: ph, nitrate, nitrite, alkaline, chlorine, and hardness.

Then I used a test kit that had all the above, plus ammonia and everything was in normal limits or 0.

How did you clean the tank? Two of the fish survived and are doing fine. I used just water to clean everything. I know to not use any kind of detergent or chemicals to clean the items. I always make sure to use the amount of chemicals/conditioners. I even added a little bit extra with this one because I had to add the conditioner before putting the plants in and then added some as I refilled the tank.

"difference in disolved solids" What?

I am thinking it was just shock. But who knows. I will definitely not do that again, even if things match I will do an acclimation.

 

[ColdKoi]

Something as much as a ph difference between the tanks could shock the fish if you just dropped them in. Could be a lot of things really, and it’s hard for anyone to say if we weren’t there and know everything that transpired. If you used a soap of any kind while cleaning the tank it’s very likely that is what caused the major loss

I don’t think it’s impossible but I wouldn’t think that a ~6month old tank would have that much stuff tied up in the substrate to nuke the tank. But I’m no expert by any means and I’ve only had much larger tanks that are generally more forgiving.

 

[Aiken Drum]

"difference in disolved solids" What?

Water has a lot of things disolved in there. Gasses, solids, other liquids could contaminate the water. There are various measures of these.

Eg. General hardness measures divalent metal ions in the water, generally magnesium and calcium. Carbonate hardness measures the amount of carbonate and bicarbonate in the water. Total disolved solids (TDS) measures the amount of every solid disolved in there, but with no distinction of what it is. Go get your water report from your water company and it should have a pretty complete list of everything in the water. It could be pages long.

Your tapwater will be a baseline, and then things in the tank can disolve in the water and give you different amounts of disolved solids in different tanks. Eg if one tank has a lump of limestone in it, this will disolve and increase both general and carbonate hardness, compared with another tank that doesnt have limestone in it. Or, maybe one tank is well established but neglected. Some things would just build up because they arent getting removed with water changes and may cause an increase in GH for instance, others will get depleted because they arent being replenished with water changes and may cause a drop in KH for instance. This is what causes "old tank syndrome". This difference in disolved solids might not be noticable with the tests you are carrying out and if big enough then it could cause shock in the fish if moved without any acclimatisation process.

Your fish dying could be nothing to do with water parameters and they would have died regardless of being moved. We dont have a TARDIS and cant find out. If they died because of the move, then something in the water caused that. Without information all anyone can do is speculate.

 

[BarbaraME]

. If you used a soap of any kind while cleaning the tank it’s very likely that is what caused the major loss

I know not to use soap or anything other than water to clean the tank and decor and gravel.

Yes, a nano tank gets pretty dirty in the gravel in a six month period. I generally do a thorough cleaning every 6 months. I was just a few weeks earlier because of the spike in the nitrite.

 

[BarbaraME]

Thank you for the explanation of dissolved solids.

And thanks everyone for the information and suggestions. The two remaining fish and my snails are doing fine and the sulfur smell is completely gone. Yep, have no idea why the fish died. Since the parameters matched exactly between the two tanks, then it could have just been shock, for some reason.

I will be restocking the tank over the 4th of July weekend. Thanks again, Barbara