Big Fish Kill - What could be the cause?

thedavman009

About a year ago I purchased a tropical aquarium, waited until the water had fully cycled and slowly began adding fish, continually checking the ammonia, nitrate and nitrite. Fast forward to Sunday and I did the weekly 10litre water change. The aquarium contains 70 litres in total.

I keep two buckets which have only been used for water changes, one to remove water and one to add. On Saturday I filled the bucket I use to add water and left it sit overnight. Sunday evening I added water conditioner to this bucket, left a further 30 minutes and then removed a bucket of water from the tank and poured in the 'add' bucket.

Almost immediately after the water change our red clawed crab died which was disappointing. Apart from that the fish looked fine. When I returned from work yesterday we had lost all our tiger barbs, green barbs, a dennison barb, an angel and our pleco, about 8 fish in total. The few remaining fish looked very distressed.

I removed the dead fish and immediately did a further 10 litre water change. The remaining fish seemed ok again after this and were fine this morning.

I am completely in the dark about what could cause such a fish kill. Ammonia, nitrate and nitrite were all ok last night although one of the remaining angles looked like the gills were slightly red which I think can indicate ammonia poisoning.

Am I ok to continue with the tank or should I restart and recycle. I have a spare home for the fish if necessary for a few weeks. What was the cause of the sudden fish kill?

kylith

Do you bring the water up to temperature before adding it?

Also, you should really change 50% of the tank water (35L) per week.

thedavman009

I leave the bucket beside the fire to heat the water but it would not be as hot as the aquarium. There is a minimal temperature movement when I do a change.

I thought a 50% water change would wipe out the beneficial bacteria and likely cause the tank to recycle?

Thanks for responding.

kylith

thedavman009 wrote: »

I leave the bucket beside the fire to heat the water but it would not be as hot as the aquarium. There is a minimal temperature movement when I do a change.

I thought a 50% water change would wipe out the beneficial bacteria and likely cause the tank to recycle?

Thanks for responding.

It would only harm the BB if you're not using dechlorinator. I see that you say that you use water conditioner. What are you using? Is it a dechlorinator? I know that a lot of people leave the water as you do to allow chlorine to evaporate but I've never been fully confident of that method myself.

It's possible that something has gotten into the water supply which is what did the damage.

thedavman009

I used API Stress Coat which is the same conditioner since the day we bought the aquarium. It removes chlorine and chloramines.

Is there a better conditioner which I should change to?

kylith

It sounds to me like it's most likely that either there was something that isn't usually present in your water supply, or something got knocked/spilled into the water in the bucket as it sat out overnight.

thedavman009

It is highly unlikely that anything got into the water between filling the bucket and pouring into the tank the following day. Maybe there was something in the water direct from the tap that was not present before!

Presuming the few remaining fish are ok this evening should I do another water change or wait until the weekend to conduct the weekly change?

Is there anything else I should do? I don't want to lose the fish, some of which we have had a year now.

Thanks for your assistance.

kylith

Personally I'd do maybe a 25% water change, but in your case I'd be loathe to recommend it in case it is something in the water. I know the fear of losing fish you've had for a while.

thedavman009

Just to update - No more dead fish yesterday evening although the silver dollar is not looking the best. I don't know how to describe it but it almost looks like his is loosing his slime. I did another 10 litre water change and included a double dose of API Stress Coat.

Should I do anything further with the tank apart from give it time?

godtabh

If you leave the water over night the chlorine dissolves out of the water.

thedavman009

I always leave the water to sit overnight, then add the conditioner shortly before pouring into the tank.

kylith

I'm afraid I'm not great with diseases, or how to advise you further. Someone more knowledgeable here might be able to help, or you could check out the Irish Fish Keepers forum.

uck51js9zml2yt

I always did a 50% weekly change a dedicated added some warm water to the business buckets to take the child off.

10l sounds very little to have any real effect on the levels.

Ranchu

Are your test kits in date. You generally get six months out of them once opened.

Did you wash your filters out when doing your water change?

thedavman009

To be honest I have not checked the date on the test kits. I never thought of it. They are definitely over 6 months old. Will check this evening.

About every second water change I will squeeze one of the four filter sponges out into the water I have removed from the tank and rotate it to the bottom so each sponge will be squeezed out over the space of 8 weeks.

Unfortunately the silver dollar was dead yesterday but the others seem absolutely fine again thankfully.

Going to bring a water sample to Sea Horse as soon as I can. I don't want this to happen again.

CruelCoin

thedavman009 wrote: »

I thought a 50% water change would wipe out the beneficial bacteria and likely cause the tank to recycle?

Thanks for responding.

When you have suspected contaminents in the water, you should be doing a massive water change (80%+) to thin out any contamination.

Maybe you had detergent on your hand, paint, methylated spirits, who knows, but something is in that water....
Best thing for you is a massive water change and add a carbon pad or two to the filter to remove contaminents.

The vast majority of the bacteria live in the filter media, not in the water.
You can do regular large water changes fairly often, providing you don't disturb the media.

thedavman009

CruelCoin wrote: »

When you have suspected contaminents in the water, you should be doing a massive water change (80%+) to thin out any contamination.

Maybe you had detergent on your hand, paint, methylated spirits, who knows, but something is in that water....
Best thing for you is a massive water change and add a carbon pad or two to the filter to remove contaminents.

The vast majority of the bacteria live in the filter media, not in the water.
You can do regular large water changes fairly often, providing you don't disturb the media.

Thanks CruelCoin.

I have not got a clue what could possibly have got into the water but I will be much more careful going forward. Absolutely do not want a repeat.

Berserker

Firstly, it could be the water OP. I live in Dublin West and our water has been dreadful lately. PH has fluctuated between 6.5 and 8. Nitrates have been rising and dropping lately too. It could be your tap water.

kylith wrote: »

Also, you should really change 50% of the tank water (35L) per week.

I was always told that you should do a 10% water change every week. I do 20L, for ease of measurement, in my 180L. I used to take more and the staff at the aquarium (Seahorse) told me to keep it at 10%.

thedavman009 wrote: »

The aquarium contains 70 litres in total.

When I returned from work yesterday we had lost all our tiger barbs, green barbs, a dennison barb, an angel and our pleco, about 8 fish in total. The few remaining fish looked very distressed.

Is that not an awful lot of fish for a 70L tank? Denison barbs and angels need a far bigger tank. That could be part of the problem also.

Ranchu

Berserker wrote: »

I was always told that you should do a 10% water change every week. I do 20L, for ease of measurement, in my 180L. I used to take more and the staff at the aquarium (Seahorse) told me to keep it at 10%.

There's no reason why you couldn't do a much larger water change. What was the reason they gave for only doing 10%?

CruelCoin

Ranchu wrote: »

There's no reason why you couldn't do a much larger water change. What was the reason they gave for only doing 10%?

Seems small to me also.

Most resources will advise 20-30% weekly

Ranchu

CruelCoin wrote: »

Seems small to me also.

Most resources will advise 20-30% weekly

How heavily stocked the aquarium is should dictate the amount of water that needs to be changed to keep your nitrates at an acceptable level.

That's how I'd look at it anyway. There's no way 10% once a week would be enough for any of my aquariums without the nitrates reaching a dangerous level over time.

Berserker

Ranchu wrote: »

What was the reason they gave for only doing 10%?

The rate at which my nitrates were increasing. My aquarium isn't heavily stocked.

Ranchu

Berserker wrote: »

The rate at which my nitrates were increasing. My aquarium isn't heavily stocked.

You generally want to keep your nitrates low though. It's highly unlikely you were eliminating all your nitrates by doing larger water changes.

denismc

The fish you describe are all quite hardy in my experience. It sounds like something fairly potent got into the water somehow, could someone else have used that bucket without you knowing. Maybe you should get the tap water checked out, their maybe some chemical or bacteria in the tap water . Maybe contact your water supplier and see if they are having problems.

Berserker

Ranchu wrote: »

You generally want to keep your nitrates low though. It's highly unlikely you were eliminating all your nitrates by doing larger water changes.

My nitrate levels are low due to the low stock level in the aquarium.

Ranchu

Berserker wrote: »

My nitrate levels are low due to the low stock level in the aquarium.

I get that but they couldn't be so low that doing a larger than 10% would be detrimental to your aquarium.

Judging by your list of fish and the size of your aquarium I would call that a heavily stocked tank unless your fish were very very small.

Either way as you suspected in your first post it is quite possibly exposure to ammonia that caused the issue.

Berserker

Ranchu wrote: »

I get that but they couldn't be so low that doing a larger than 10% would be detrimental to your aquarium.

Judging by your list of fish and the size of your aquarium I would call that a heavily stocked tank unless your fish were very very small.

Ok, you guys are starting to worry me now. I have 14 tiger bars (7 green & 7 albino) in my 180L. I had a cabinet reshuffle a while ago, as I was worried about aggression in the future. All are 1 inch or less in size. Some of my green tigers are tiny.

Each week I test my water and I get 0ppm ammonia & nitrites consistently. Nitrates tend to be in or about 20ppm. It was based on these figures that I was told to do a 10% change. So, should I change more? My tank has quite a few live plants in there too.

Sorry for hijacking the thread OP.

Ranchu

Berserker wrote: »

Ok, you guys are starting to worry me now. I have 14 tiger bars (7 green & 7 albino) in my 180L. I had a cabinet reshuffle a while ago, as I was worried about aggression in the future. All are 1 inch or less in size. Some of my green tigers are tiny.

Each week I test my water and I get 0ppm ammonia & nitrites consistently. Nitrates tend to be in or about 20ppm. It was based on these figures that I was told to do a 10% change. So, should I change more? My tank has quite a few live plants in there too.

Sorry for hijacking the thread OP.

Sorry I have got you and the op mixed up!

Your parameters look fine. Your tank is definitely not overstocked. 14 tiger barbs in a 180 will be fine. They possibly told you to only do 10% as the nitrates will benefit your plants.

CruelCoin

Berserker wrote: »

Each week I test my water and I get 0ppm ammonia & nitrites consistently. Nitrates tend to be in or about 20ppm. It was based on these figures that I was told to do a 10% change. So, should I change more? My tank has quite a few live plants in there too.

You should be doing changes for more than just Nitrates.

Hormones build up in the water, as do organic wastes, general polutants, etc.

thedavman009

Glad to report that the aquarium has returned to normal and all the fish are swimming happy again. I am still none the wiser as to what might have got in the water but going forward I think I will keep the 'in' bucket covered as it sits overnight. Also going to conduct twice weekly 10% water changes.

Thank you to all for the posts and input.

CruelCoin

thedavman009 wrote: »

Glad to report that the aquarium has returned to normal and all the fish are swimming happy again. I am still none the wiser as to what might have got in the water but going forward I think I will keep the 'in' bucket covered as it sits overnight. Also going to conduct twice weekly 10% water changes.

Thank you to all for the posts and input.

Best of luck with it