Disaster! Help!!

[Cromid]

what is happening!

Overnight 4 of my rainbow fish, two tetras an rasbora a Cory and my lovely angelfish have died.

I have no idea what has happened or why.

I’ve never seen anything like this or ever had this problem. One of the rainbows was at the surface a lot last night, so I quarantined it but that was it. What the hell could have ravaged a tank this quickly?

I’ve just seen that my test kit is out of date so I’m worried I’ve not noticed a potential problem, and can’t give then accurate readings, so have a replacement one on order.

Currently doing a 50% water change. What could have done this?

Temp steady at 76. I guess I’ll need to wait for the test kit replacement to get accurate readings in the rest.

Could it be a parasite?

 

[Magnum Man]

we'll need more information, about how long the tank has been set up, what your water is "normally" got kids or other well meaning, that could have put something in the tank... water change lately without chlorine remover??? worked on the tank lately with lotion on your hands???
it would have to be something drastic to kill them allover night... are there any fish left that didn't die???

 

[GaryE]

You're doing what you can. If something goes awry, water change first, ask questions after.

Look very closely at the fish to see if there are sores, or skin parasites. In dim light, shine a flashlight along their spines and look for a velvety texture. That's all you can do - check for ich, velvet or an obvious bacterial cause.

An ammonia spike can do that. A toxin getting into the water can. If you overcrowded the tank, tanks will crash. Going too long between water changes will do it. Those are the reasons why aggressive water changing NOW is the best first line response. There are things that can go wrong that test kits won't tell you about - they are very limited tools.

 

[Cromid]

we'll need more information, about how long the tank has been set up, what your water is "normally" got kids or other well meaning, that could have put something in the tank... water change lately without chlorine remover??? worked on the tank lately with lotion on your hands???
it would have to be something drastic to kill them allover night... are there any fish left that didn't die???

Sure, hopefully the water testing kit arrives soon and I can test more accurately and test for ammonia. But from just the small test strips I have the ph 7. Kh 80. Gh 120. Nitrite 0. Nitrate 20.
I always use seachems declorinator on water changes.

Tank has been set up for 2 1/2 years after a house move. Couple of cories and tetras introduced two weeks ago. Majority of the deceased fish aren’t new, the rainbows are 4 years old, the rasbora was 6.

But yes there’s still plenty fish alive. All my rummynose tetras are fine. Siamese algae water and pearl goruami.

Couple of new plants introduced last week.

I did turn the flow rate down alittle a few weeks back, as most of the tetras seemed to hang about in a certain area and I thought the flow was perhaps too much for them. Since doing this they were moving around the tank more.
My worry now though is that the flow was too low, and surface agitation wasn’t enough, so oxygen levels have been dropping. I did see as I say that rainbow gasping at the surface last night. And maybe why the fish died overnight when oxgyenation drops further and co2 production is up.
It’s also been very warm here the past couple days with a start of a heatwave. I maybe this has dropped that o2 level even further.

i have done a large water change today. Turned the flow back up. And think I will add an airstone.
I’ve ordered a better outlet diffuser to direct the water up to the surface too.

 

[Cromid]

You're doing what you can. If something goes awry, water change first, ask questions after.

Look very closely at the fish to see if there are sores, or skin parasites. In dim light, shine a flashlight along their spines and look for a velvety texture. That's all you can do - check for ich, velvet or an obvious bacterial cause.

An ammonia spike can do that. A toxin getting into the water can. If you overcrowded the tank, tanks will crash. Going too long between water changes will do it. Those are the reasons why aggressive water changing NOW is the best first line response. There are things that can go wrong that test kits won't tell you about - they are very limited tools.

Thanks. Yeh I’ve been checking the fish for any signs of parasites or disease.
Nothing that I can see apart from a tiny black speck that seems to protruding out of one of the gills of the decease rainbows, so not sure what that is, but to have no other sign of any disease on fins/gils it does feel strange to have them succumb so quickly.

I’m anxious to test for ammonia spiking. Hopefully the water changes will be enough to keep any potential spike down now until I test

 

[GaryE]

Watch, because unquarantined new fish can bring nasty surprises. Often they will have survived something the fish in the tank will never have met up with, and that can wipe out established species while the new fish are unaffected. The world of fish viruses is poorly studied.

We tend to think of quarantine as being for the new fish, but new fish can also be carriers. I like to give any farm raised fish a good period for pathogens to die off in them, as I have seen things like you're describing. Not everyone has the resources to do that, but there is an element of Russian roulette with new fish in the first 6 weeks.

 

[Cromid]

Watch, because unquarantined new fish can bring nasty surprises. Often they will have survived something the fish in the tank will never have met up with, and that can wipe out established species while the new fish are unaffected. The world of fish viruses is poorly studied.

We tend to think of quarantine as being for the new fish, but new fish can also be carriers. I like to give any farm raised fish a good period for pathogens to die off in them, as I have seen things like you're describing. Not everyone has the resources to do that, but there is an element of Russian roulette with new fish in the first 6 weeks.

Ah, very rough lesson learned if that is indeed the case. Hopefully they’ll be no more over the next few days/week. If there is I unfortunately see this entire tank crashing which will be such a shame.

 

[Colin_T]

You probably poisoned them yesterday. What did you do to the tank on the day before they died?

 

[GaryE]

If nothing toxic (sprays, cleansers/air fresheners) got into the tank, I find those things can flare and vanish. They often don't wipe the tank out, but do take larger and more fragile fish and have an uncanny way of showing you your overcrowding, if that's what you do (sometimes I do....).