I vacuumed my tank. Now everyone is dying.

[Paula Blanca]

I am SO upset! I've had a 29 gallon, heavily planted, up and running with the same 4 fish for a year. A flame gourami, 2 otos and a siamese algae eater. I've not changed anything in months. The plants do a good job of keeping nitrates down so I usually top off the tank and then vacuum about once a month. I vacuumed with the same vacuum I always use about 30% of the water 3 days ago. I used stress coat to dechlorinate. Other than poking a few loose plant roots back in to the sand I changed nothing. Today I have a dead oto, a dead SAE and my gourami is definitely going to die. The last remaining oto is so hard to find that he may be dead soon too.  What did I do to cause this mayhem!!!?!  .25 ammonia, 0 nitrite, 0 nitrate. The only thing I didnt test was pH but I'm always right at 7.2 so unless disturbing the sand caused something to be released I am at a total loss. THe fish seemed fine yesterday and the day before. The gourami started being weird today and thats when we found the recently dead oto and algae eater. No white marks, not fungus, no clamped fins, no hemorraging, no holes, no missing scales. Perfectly normal looking fish except for the dead part.

[xXInkedPhoenixX]

I'm very sorry for your losses @Paula Blanca. You didn't say if vacuuming (disturbing substrate) is something you normally do. If it isn't sometimes sadly yes this can cause issues in your tank. The other possibility is that maybe there is a dead fish in the tank causing the ammonia did you see the missing Oto before the vacuuming event?

I would do a large water change to get ammonia to 0 immediately- your fish could potentially be saved. If you have extra airstones that can help. You might want to hold back on feeding until ammonia consistently tests at 0

Also, do your best to account for any missing fish or snails if you have them, they can be the culprit if they have passed.

Edited April 3, 2022 by xXInkedPhoenixX

[Paula Blanca]

I have sand so I usually just hover the vacuum over the surface. I vacuum once a month. The thing I did differently this time was poke a couple of plants a little deeper in to the sand. I did notice the water was cloudier longer than usual after the cleaning and then today everyone dropped (floated?) dead and the water still seems cloudy.

Both the oto and the siamese algae eater corpses were in great condition. They hadn't started decomposing at all.  The algae eater had a little bit of slough above his lip but that was the only thing that made him look anything other than perfectly healthy sleeping fish.  The other oto I thought was dead months ago - so now that the gourami is about to biff it I'm going to be stuck with another dead fish hunt because that is one super sneaky oto and I doubt he's going to live when 3 others died.

What I think I want to do is rescape - I need to move some plants - treat the entire tank with fungal and bacterial meds and then restock (I prefer low stocked tanks). But my fear is that whatever happened in the substrate could happen again, or maybe that wasn't the issue at all anyway although unless my water suddenly had a massive pH swing from the tap (it's back to 7.2 now) I cannot figure out what the heck happened. Oh, and my temperature is steady too.  

Could I have gotten some sort of tainted stress coat?  I put in the recommended amount to my bucket before I added it to the tank.

 

[modified lung]

There's been twice I kicked up some sand in one of my tanks and a series of fish deaths followed. Both times were after a larger than usual snail feeding. My guess is the cloudiness from the sand + small amounts of ammonia together at once is what did it in my tank because one of those two issues alone doesn't cause any problems.