Fish floating heads up and dying one by one

I got 12 white cloud mountain minnows yesterday. After 5-6 hours I noticed one staying near the surface, its tail would sink down, it would swim and right itself, and repeat. After a few hours it seemed to get stiffer. Eventually it started sinking like it was paralyzed, it would give a few twitches and right itself again near the surface, and repeated until it died. Later when I went to sleep I noticed another hanging out near the surface, tail starting to droop. When I got up it had died also. I get home from work today, and there's a third fish dead. Now I have a fourth, hanging out with its head near the surface, tail drooping, and every once in a while it just starts to sink like its paralyzed.

This is a fairly new tank. Two weeks ago I filled it and put in some plants, as well as cleaned off an old filter in the water for bacteria. Last week I put in 4 Amano shrimp. They were acclimated fairly slowly, and everyone seems fine, except for these 4, which are all different sizes. Seeing the last one looking ill, I just did a 25% water change. I have tap water which I condition.

If anyone can help me out and save the fish that would be great!

 

It sounds like the tank isn't cycled you should watch this video about the nitrogen cycle.

To combat this you are going to need to do daily water changes until the tank is cycled you should also get nitrate test kits and test the water every few days.

 

Are you testing your water? It sounds like they are suffocating! Cleaning an old filter with tank water won’t re establish old beneficial bacteria. What was in an old filter is long dead.
You either have high ammonia or low oxygen if they are at the surface.

 

And jump starting a tank with old filter media debris doesn't cycle the tank all it does it add starter bacteria to the tank you added too many fish at once. The bacteria needs to grow enough first so it can handle the load in the tank.

 

And jump starting a tank with old filter media debris doesn't cycle the tank all it does it add starter bacteria to the tank you added too many fish at once. The bacteria needs to grow enough first so it can handle the load in the tank.

Will it add starter bacteria? Sounds like it was an old dried out filter to me.

 

Will it add starter bacteria? Sounds like it was an old dried out filter to me.

I'm just guessing he used a active filter cartridge from another cycled tank.

 

Thanks for the suggestions, I agree its probably ammonia or oxygen. I'm familiar with the cycling process but I'm not experienced.

The filter I used was from an old betta tank. Betta died about 9 months ago, the tank's been running ever since with a few plants and snails. Would the bacteria have died?

I thought o2 would be covered because of the number of plants and the filter. I've just turned the air stone back on.

I've had some rotting plant matter in the tank for 2 weeks, and some uneaten shrimp food for 1. Did I jump the gun by adding too many fish at once? I also put in 3 oto cats which seem to be fine.

What makes me question it being o2 or poisoning though is that 4 out of 12 have died, spaced out 1 by 1 over 24 hours. I'm not experienced but it seems like they'd all show signs. Is my rationale wrong?

 

It hasn't been cycling with plants. The cycle needs ammonia to feed bacteria. Plants don't give off ammonia. The bacteria would have died out.

As others have mentioned, you should test your water. It's impossible to say for sure, but everything you've said sounds like a classic case of ammonia poisoning, in this case, new tank syndrome.

I'd recommend aggressive water changes until you get this figured out. I'd start with a 50% water change, then at least 25% a day until you get a handle on your test parameters. I'll bet with aggressive water changes you'll start seeing improvements.

 

Ok my bad! I assumed you meant a dried out filter. But I’m not sure if the Betta tank running saved the BB! That would be for someone more experienced. In the meantime though.... if you don’t have a way to test the water, do am immediate 50% or more water change. And do this daily until you know what your water parameters are. With every WC you cut the ammonia in half.

 

Thanks guys, I was thinking that the plants and snails would keep the bacteria going but that makes complete sense.

Looks like I'll be changing water, aggressively!

 

Thanks guys, I was thinking that the plants and snails would keep the bacteria going but that makes complete sense.

Looks like I'll be changing water, aggressively!

Like right now! It’s better to be safe than sorry. Some fish are stronger and will hold on for a little while. But until you know for sure, assume it’s ammonia. They can’t breathe.

 

If there was any beneficial bacteria left in the filter media, it was only enough for some snails, not enough for all of the fish, so it wasn't quite enough to instant cycle.

Get yourself some Seachem Prime, itll render ammonia harmless under 1ppm while allowing your new filter media to process the cycle uninterrupted. Do 50% water changes each time you reach 0.50-1ppm ammonia to help your cycle complete. Dose with Prime every 48 hours regardless of water change or not. Also use Prime on new water.

Its tough, but you can do it. If possible, if you know a friend with a tank, or even if you're on good terms with the store, see if you can get some used filter media. If you can, ADD it to your filter. Dont just squeeze it. Actually use it

 

If you're cycling with media from a snail tank you do have bb. Just not enough.

What id do is don't add fish but start gradually feeding your tank. Ammonia doesn't actually come from the fish but rather its poop.
Decaying fishfood and fish poop is essentially the same so by gradually building up to adding the volume of food you will need to feed whichever fish you plan to add you can get the bb up to the correct population prior to adding the fish.

Its abit hard to explain but in short if you feed the imaginary fish for a month before adding in the real thing the tank will cycle as if you did a fish-in cycle without risking the fishes health. And the bacteria won't experience any changes when you do add it.

I prefer whenever possible to do this even if I'm using established media just to make sure I get no spikes whatsoever after the addition of fish.

 

So I'm changing out the water, I got my air stone on, I got a test kit and everything's within parameters- but I had another fish die last night and now another is hanging out at the surface, moving just enough to prevent its tail from drooping down too low.

I have to say also, it looks pretty bloated. Could I be overfeeding them? Could it be constipated? Should I feed it some frozen peas?

 

So I'm changing out the water, I got my air stone on, I got a test kit and everything's within parameters- but I had another fish die last night and now another is hanging out at the surface, moving just enough to prevent its tail from drooping down too low.

I have to say also, it looks pretty bloated. Could I be overfeeding them? Could it be constipated? Should I feed it some frozen peas?

What are your test results? What test kit did you get? What size tank is this?

 

API freshwater master test kit. The ammonia was .5 ppm this morning. I've been changing it every day except yesterday, so .5 should be the upper range that they've been experiencing. It's a 29 gal tank.

 

Sounds like sick incoming non-quarantined fish are dying from the stress of moving.

I would see if you can exchange the dead/dying fish back with the store.

The next step on your end will be to implement a new incoming fish quarantine process.

Check out this video... Especially the part about nearly all fish showing up from the importers/wholesalers having some problem like tape worms and such.