Aquarium suddenly died off?

[Amayapuppy]

Hello! I have a 15 gallon externally filtered [canister] aquarium that had a school of glowlight tetras, otocinclus, blue rasboras and one betta. The tank has been going well for about 6 months until about a week ago when I added one last glowlight tetra to complete the school who didn't have any visible symptoms. Since then, the entire aquarium except my school of glowlight tetras has died, showing no visible symptoms of illness minus gasping (despite my aerator and surface disruption). I have no idea what could've caused this and what I could have done to avoid it, I have yet to see a single dead fish and all of my parameters are testing 0 (the aquarium is heavily planted, so the nitrates always test very low). Could anyone guide me into knowing why I lost like 13 fish suddenly? Can the glowlight tetras be carrying an illness that effects other fish but not themselves? Thank you! I also read that an oil heater I recently added to my room couldve caused an issue, but my other two aquariums are completely fine and I couldn't find any more information on that, but I thought I'd throw it in.

 

[Colin_T]

Pictures and video of the fish?
Upload videos to YouTube, then copy & paste the link here.

Just clarifying, you added 1 new glolight tetra and a few days later the other fish in the tank started dying.
All the fish in the tank except the glolights have died.
The glolight tetras are gasping/ breathing heavily but show no other symptoms?

What symptoms (if any) did the other fish show?

Did you add anything else (besides the new glolight tetra) to the tank in the 2 weeks before this started?
Did you do a water change or clean the filter or do anything to the tank just before this started?
Did you have any visitors the day before this started (someone might have put something in the tank)?

Do you have buckets that are used specifically for the fish?
Do you have hoses/ gravel cleaner, etc, that are used specifically for the fish?

Do you use hand sanitiser, moisturising creams, perfumes, or anything else that might leave a residue on your skin?
Does anyone smoke, paint, or use any type of aerosol (perfume, hair spray, deodorant, etc) in the room?

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Basic First Aid For Fish
Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.

Do a 75% water change and gravel clean the substrate every day for a week or until the problem is identified. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in. It also removes a lot of the gunk and this means any medication can work on treating the fish instead of being wasted killing the pathogens in the gunk.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens so any medication (if needed) will work more effectively on the fish.

Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.

 

[Amayapuppy]

Pictures and video of the fish?
Upload videos to YouTube, then copy & paste the link here.

Just clarifying, you added 1 new glolight tetra and a few days later the other fish in the tank started dying.
All the fish in the tank except the glolights have died.
The glolight tetras are gasping/ breathing heavily but show no other symptoms?

What symptoms (if any) did the other fish show?

Did you add anything else (besides the new glolight tetra) to the tank in the 2 weeks before this started?
Did you do a water change or clean the filter or do anything to the tank just before this started?
Did you have any visitors the day before this started (someone might have put something in the tank)?

Do you have buckets that are used specifically for the fish?
Do you have hoses/ gravel cleaner, etc, that are used specifically for the fish?

Do you use hand sanitiser, moisturising creams, perfumes, or anything else that might leave a residue on your skin?
Does anyone smoke, paint, or use any type of aerosol (perfume, hair spray, deodorant, etc) in the room?

---------------------

Basic First Aid For Fish
Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.

Do a 75% water change and gravel clean the substrate every day for a week or until the problem is identified. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in. It also removes a lot of the gunk and this means any medication can work on treating the fish instead of being wasted killing the pathogens in the gunk.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens so any medication (if needed) will work more effectively on the fish.

Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.

Thank you for the quick response!
Video of the tetras here:

I have since found at least two of the otocinclus, which more may be in the tank its hard to tell with them. I also still have my assassin snails.

"Just clarifying, you added 1 new glolight tetra and a few days later the other fish in the tank started dying.
All the fish in the tank except the glolights have died.
The glolight tetras are gasping/ breathing heavily but show no other symptoms?"

Yes this is correct. The new tetra is the albino one.
No visible symptoms on any that I've noticed, no lethargy or weird swimming, the only pattern I noticed [before adding the albino tetra], was them suddenly schooling together which I've only seen them do when stressed.

I added two plants the day I added the fish, from the same aquatics store.

Other than checking the water and refilling the evaporated water with the same clean sink water, no.
No visitors.
Yes, I have a new aquarium bucket that has been used on every tank.
I have a gravel vaccuum I use for all three aquariums.
I do not use anything external like that, except for hand sanitizer from work, though I rarely touch my tanks after work.
No smoking/painting/etc in the room.

 

[Colin_T]

The glolight tetras do not appear to have any external diseases but they are breathing a little faster than they should be.

Did you feed them before taking the video?
Are their stomachs normally that shape?

Can you post a picture of the aquarium?
I want to see the substrate and the glass on the front of the tank. It looks like there is blue green algae (Cyanobacter bacteria) on the glass under the substrate. The plant leaves look like they have it too.

Do the plants have a green slimy film that wipes off easily?

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Sorry if this sounds weird, but do you do water changes where you remove some aquarium water and then add clean dechlorinated water, or do you just top the aquarium up when the water level drops a bit?

If you do water changes, how often do you do them and how much do you change?

Do you add aquarium plant fertiliser?
If yes, what brand, how often, how much?

What sort of filter is on the tank?
How often and how do you clean the filter?

This looks like a water quality issue but without seeing the dead fish it's not 100%. I would stop adding fertiliser for a few weeks and do some water changes to dilute anything in the tank. See how they go over a few weeks and if they are ok, then maybe start adding fertiliser again.

 

[Amayapuppy]

The glolight tetras do not appear to have any external diseases but they are breathing a little faster than they should be.

Did you feed them before taking the video?
Are their stomachs normally that shape?

Can you post a picture of the aquarium?
I want to see the substrate and the glass on the front of the tank. It looks like there is blue green algae (Cyanobacter bacteria) on the glass under the substrate. The plant leaves look like they have it too.

Do the plants have a green slimy film that wipes off easily?

------------------

Sorry if this sounds weird, but do you do water changes where you remove some aquarium water and then add clean dechlorinated water, or do you just top the aquarium up when the water level drops a bit?

If you do water changes, how often do you do them and how much do you change?

Do you add aquarium plant fertiliser?
If yes, what brand, how often, how much?

What sort of filter is on the tank?
How often and how do you clean the filter?

This looks like a water quality issue but without seeing the dead fish it's not 100%. I would stop adding fertiliser for a few weeks and do some water changes to dilute anything in the tank. See how they go over a few weeks and if they are ok, then maybe start adding fertiliser again.

I don't do water changes as much as I should be as I was under the impression if the nitrates are fine you don't need to as often, but I'm starting to understand that isn't the case anymore. Currently I just top off the water level, but I do own a siphon and gravel vacuum when something is occurring that indicates I should.
I use flourish on occasion, maybe once every couple weeks.
It's a canister filter, definitely hasn't been cleaned for a few months.
I did feed them before the video, about an hour prior.
Yes their stomachs normally appear that way.
The glotetras are now losing coloration/growing pale, I'm going to do a 75% water change today as I didn't have time yesterday.
Sorry the photos aren't great! there is also a reflection of a green tarp on the white sand.

 

[Colin_T]

Check the pH of the aquarium water and tap water and make sure they are similar before doing big water changes. If there is a big difference in pH, do small (10-20%) water changes each day until the pH is closer to the tap water, then do bigger water changes.

Water changes are essential even in planted tanks, and should be done at least once every 2 weeks.

You do water changes for a number of reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.
3) to keep the pH, KH and GH stable.
4) to dilute nitric acid produced by fish food and waste breaking down.
5) to dilute stress chemicals (pheromones/ allomones) released by the fish.
6) to dilute un-used plant fertiliser so you don't overdose the fish when you add more.
7) to remove fish waste and other rotting organic matter.

It is possible the fish died because there is too much plant fertiliser in the water. If the plants don't use it all up, before you add another dose, you can get a build up that poisons fish. Doing a big water change before adding another dose of fertiliser, will dilute any remaining nutrients and reduce the chance of an overdose.

The blue green algae on the substrate and possibly the plants is an indication of nutrients building up to high levels and the plants are not getting rid of them. Again more frequent water changes and gravel cleaning open areas of substrate would help.

At this stage, I would clean the filter and do daily water changes for a week or two and see how things look after that. If any fish die during this time, photograph them and post pics here.

 

[Aiken Drum]

2 sides to a water change. Removing old water including waste and adding new water.

Problem with just topping up evaporation is that evaporation is only removing H2O, and leaving everything else behind. So disolved substances just build up over time if you arent physically removing them with water changes. There is more than just nitrate in there.

The other side of it is carbonate hardness (KH). The nitrogen cycle uses up KH. KH is normally replenished with new water, i dont see topping up after evaporation putting as much new water in a tank as a water change. If your KH gets depleted, your cycle won't be able to function. Ammonia will build up. Also KH is what stops your pH from crashing.

 

[Amayapuppy]

Check the pH of the aquarium water and tap water and make sure they are similar before doing big water changes. If there is a big difference in pH, do small (10-20%) water changes each day until the pH is closer to the tap water, then do bigger water changes.

Water changes are essential even in planted tanks, and should be done at least once every 2 weeks.

You do water changes for a number of reasons.
1) to reduce nutrients like ammonia, nitrite & nitrate.
2) to dilute disease organisms in the water.
3) to keep the pH, KH and GH stable.
4) to dilute nitric acid produced by fish food and waste breaking down.
5) to dilute stress chemicals (pheromones/ allomones) released by the fish.
6) to dilute un-used plant fertiliser so you don't overdose the fish when you add more.
7) to remove fish waste and other rotting organic matter.

It is possible the fish died because there is too much plant fertiliser in the water. If the plants don't use it all up, before you add another dose, you can get a build up that poisons fish. Doing a big water change before adding another dose of fertiliser, will dilute any remaining nutrients and reduce the chance of an overdose.

The blue green algae on the substrate and possibly the plants is an indication of nutrients building up to high levels and the plants are not getting rid of them. Again more frequent water changes and gravel cleaning open areas of substrate would help.

At this stage, I would clean the filter and do daily water changes for a week or two and see how things look after that. If any fish die during this time, photograph them and post pics here.

This is wonderful information and very useful to know! Thank you, I will definitely do more water changes from here on out. I had asked before and googled and could never find much information on why if nitrates were low, and understanding now really helps. I already did a water change before I saw this, but from now on I'll always check the ph before big water changes. I'll clean the filter tomorrow when I have dirty water to do so!

 

[Amayapuppy]

2 sides to a water change. Removing old water including waste and adding new water.

Problem with just topping up evaporation is that evaporation is only removing H2O, and leaving everything else behind. So disolved substances just build up over time if you arent physically removing them with water changes. There is more than just nitrate in there.

The other side of it is carbonate hardness (KH). The nitrogen cycle uses up KH. KH is normally replenished with new water, i dont see topping up after evaporation putting as much new water in a tank as a water change. If your KH gets depleted, your cycle won't be able to function. Ammonia will build up. Also KH is what stops your pH from crashing.

Thank you for the information! I'll be sure to do water changes more often.