Water change caused death

[alliw]

Not sure where to post this as I did a WC and some rearranging yesterday and this morning woke up to my only fish - a black Molly - dead.

20g tank. Did a 4g water change with new salt ( was using IO orange and we to to AF sea salt)
Vacuumed much of the sandbed and moved some rocks around
Switched filters, adding some carbon to the new one to clean the water
Tried to use SEACHEM CORALCRETE to affix a coral but it disintegrated so I used aquarium glue instead

My corals are all looking great today and my blood shrimp as well.
What could have gone wrong? Did moving the rocks disturb the sandbed enough to instigate an onset of bacteria?

 

[cdnco2004]

The WC would not kill your moly unless it was contaminated with some toxin. How old was the Moly? How long have you had it? Is the tank it was in fully cycled?

 

[TX_REEF]

Not sure where to post this as I did a WC and some rearranging yesterday and this morning woke up to my only fish - a black Molly - dead.

20g tank. Did a 4g water change with new salt ( was using IO orange and we to to AF sea salt)
Vacuumed much of the sandbed and moved some rocks around
Switched filters, adding some carbon to the new one to clean the water
Tried to use SEACHEM CORALCRETE to affix a coral but it disintegrated so I used aquarium glue instead

My corals are all looking great today and my blood shrimp as well.
What could have gone wrong? Did moving the rocks disturb the sandbed enough to instigate an onset of bacteria?

how old is the system and when did you last clean the sandbed? vacuuming the entire sandbed is generally a no-no unless you're doing it on a regular basis; you could certainly have disturbed gases/bacteria in the sand bed. Your molly would have been the most oxygen-dependent animal in the tank so it's not super surprising if he got hit the hardest.

 

[alliw]

The tank has been running since March. The Molly was added in May and the shrimp in August. I normally vaccum only 1/4 of the sandbed but hadn’t done the back portion as the rocks were too tight to the glass to get in there which is why I moved them

 

[TX_REEF]

I wouldn't recommend cleaning like that again, stick to your 1/4 per instance (or add sandbed-stirring critters and leave the sand alone) and avoid rearranging if possible - saltwater systems like stability! It seems to me that stirring your entire sandband could have rapidly reduced oxygen in the water.

 

[cdnco2004]

How was water circulated in the tank? Good gas exchange via surface agitation? Stired up bacteria as stated "could" starve your moly of oxygen but I think that is a stretch for a tank with only 1 molly. I was breeding mollies for SW and had a 75 gallon with 40 mollies in it. Some how the air line popped out of the tank and it only had the internal power head circulating water and it was NOT pointed at surface, and the next day the mollies were still alive. I seriously doubt stirring up the bed caused that large of a bacterial bloom that it striped the tank of O2. Also OP was there a bacterial bloom?

 

[alliw]

How was water circulated in the tank? Good gas exchange via surface agitation? Stired up bacteria as stated "could" starve your moly of oxygen but I think that is a stretch for a tank with only 1 molly. I was breeding mollies for SW and had a 75 gallon with 40 mollies in it. Some how the air line popped out of the tank and it only had the internal power head circulating water and it was NOT pointed at surface, and the next day the mollies were still alive. I seriously doubt stirring up the bed caused that large of a bacterial bloom that it striped the tank of O2. Also OP was there a bacterial bloom?

I had everything turned off while I was cleaning except the light, so no water circulation at the time and yea the tank looked cloudy. A few weeks ago I posted on here about something that some members thought may be bacteria so I removed the rock that it was seen on and it hasn’t gone back into the tank but now I’m thinking that the bacteria could’ve still been present and not visible?
What can I do to make sure there is no bacteria?
Should I have left a power head on durning cleaning?

 

[alliw]

I wouldn't recommend cleaning like that again, stick to your 1/4 per instance (or add sandbed-stirring critters and leave the sand alone) and avoid rearranging if possible - saltwater systems like stability! It seems to me that stirring your entire sandband could have rapidly reduced oxygen in the water.

Lesson learned. Would having a sand sifting goby help? Or would it die from sifting sand that’s unhealthy? I assume it would’ve died because of my clean as well.

 

[TX_REEF]

Lesson learned. Would having a sand sifting goby help? Or would it die from sifting sand that’s unhealthy? I assume it would’ve died because of my clean as well.

sand sifting gobies are good for that, as are nassarius snails. The speed at which they turn over the sand is slow enough that they won't cause a major disruption like we can as humans stirring it all up at once. It's not that your sand is unhealthy, it just isn't meant to be stirred up all at once. I personally have never manually stirred my sand.

 

[alliw]

sand sifting gobies are good for that, as are nassarius snails. The speed at which they turn over the sand is slow enough that they won't cause a major disruption like we can as humans stirring it all up at once. It's not that your sand is unhealthy, it just isn't meant to be stirred up all at once. I personally have never manually stirred my sand.

Thanks. Still learning (the hard way). Appreciate your insight. So you think it was that rather than the new filter with rinsed carbon or the epoxy? I feel like Mollys are next to indestructible but I guess something like bacteria could kill it fast or lack of oxygen as was mentioned

 

[TX_REEF]

Carbon can cause HLLE when used improperly but that would certainly not happen that fast, so definitely not the carbon. I’ve used all sorts of epoxy and super glues in my tank and none of my fish or corals ever complained, so I doubt that as well

 

[cdnco2004]

I had everything turned off while I was cleaning except the light, so no water circulation at the time and yea the tank looked cloudy. A few weeks ago I posted on here about something that some members thought may be bacteria so I removed the rock that it was seen on and it hasn’t gone back into the tank but now I’m thinking that the bacteria could’ve still been present and not visible?
What can I do to make sure there is no bacteria?
Should I have left a power head on durning cleaning?

But you turned all the equipment back on after you did the WC right? And it will get cloudy looking because you stirred up the sandbed but if it settled right back down and was clear by morning or was it still very cloudy?

 

[alliw]

But you turned all the equipment back on after you did the WC right? And it will get cloudy looking because you stirred up the sandbed but if it settled right back down and was clear by morning or was it still very cloudy?

Yes, as soon as I finished up and it cleared quickly probably in 20mins and by cloudy I mean at the worst moment I could still easily see what I was doing, not like a blizzard lol

 

[cdnco2004]

Yes, as soon as I finished up and it cleared quickly probably in 20mins and by cloudy I mean at the worst moment I could still easily see what I was doing, not like a blizzard lol

If it cleared up by morning than it was not a bacterial bloom. This more than likely will be one of those instances where you will just never know. I have done full sandbed cleanings never had that result. I just don't see oxygen depletion it unless it created a large bloom. Do you have a skimmer on that tank?

 

[alliw]

Carbon can cause HLLE when used improperly but that would certainly not happen that fast, so definitely not the carbon. I’ve used all sorts of epoxy and super glues in my tank and none of my fish or corals ever complained, so I doubt that as well

The Seachem stuff was so brittle it basically crumbled apart in the water even after I kneeled it profusely. I’d only just bought it but threw the rest out based on this

 

[alliw]

If it cleared up by morning than it was not a bacterial bloom. This more than likely will be one of those instances where you will just never know. I have done full sandbed cleanings never had that result. I just don't see oxygen depletion it unless it created a large bloom. Do you have a skimmer on that tank?

I had a HOB coralife skimmer on it but didn’t put it back in yesterday, I’m not sure it was doing much but collect water. It was sitting correctly etc so I did get bubbles but with only one fish, what was I skimming for?

 

[Idech]

If you never disturbed the sand, or if you did it deeper than usual and everywhere, this releases anaerobic bacteria that will die in contact of oxygen and create an ammonia spike.

This is unfortunately a common cause of killing fish in unsuspecting fish keepers.

Either disturb the sand regularly, or don’t do it at all or very sparingly.

 

[alliw]

If you never disturbed the sand, or if you did it deeper than usual and everywhere, this releases anaerobic bacteria that will die in contact of oxygen and create an ammonia spike.

This is unfortunately a common cause of killing fish in unsuspecting fish keepers.

Either disturb the sand regularly, or don’t do it at all or very sparingly.

That was my first thought as well. I did the back and I dug deep as it hadn’t been cleaned yet (March). I just wanted to get rid of the diatoms and some of the tube worms.
I did an ammonia test this morning as soon as I found and retrieved the deceased fish and it was close to 0. I have the API for that test and a Seachem patch that was yellow so do I need a Hanna checker? I know even a bit of ammonia could hurt the fish but I’ve seem Mollys live in filthy tanks. I couldn’t have possibly removed alllllll my good bacteria

 

[Idech]

I did an ammonia test this morning as soon as I found and retrieved the deceased fish and it was close to 0.

The ammonia spike doesn’t last very long so if you test the next day, your bacteria will have taken care of it.

I couldn’t have possibly removed alllllll my good bacteria

No, you didn’t remove it, just fed it with ammonia !

 

[alliw]

The ammonia spike doesn’t last very long so if you test the next day, your bacteria will have taken care of it.

No, you didn’t remove it, just fed it with ammonia !

SMH. That’s one way to ensure you have the good bacteria happening. I didn’t know that. now I need to figure out what to do if there’s an ammonia spike again. Good to know it didn’t affect the corals or shrimp though. Just sadly, I killed my fish.