Fish Dying Quickly

ccmman

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Hello,

We have a 35 gallon tank. The last group died off slowly. Nothing out of the ordinary. We cleaned the tank, out in a new filter, and bought 12 new fish. All died in matter of days. It seemed like they were gasping for air at the top of the aquarium. Our home water test beforehand didn’t yield anything out of the ordinary. After the fish died, we replaced about 50% of the water. Test at Petsmart looked good ... twice. We got a smaller group of fish. Things didn’t look good again (fish at surface apparently gasping), so I added stress-zyme. It seemed to help, but not for 3 of the smaller fish. The three larger ones hanging on.

The water heat is about 78 and the sole plant I bought a week ago looks to be in tough shape. I also slacked on water changing when we were down to one fish prior to the 50% water change. From what I’ve read, my gut is we are low on oxygen, but It doesn’t show up in the water test and I don’t know why we’d be low.

Thoughts?
 

tellin

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Maybe oxygen is low because your filter is too small for your tank? Or perhaps not functioning properly? How many gallons is it rated for?

I'm sure you lost your cycle when you changed your filter, unless you took a couple of months to re-establish the cycle before putting the new fish in. It seems like it should take more than a few days for 12 fish to pollute a 35 gallon, though. What were your ammonia/nitrite/nitrate levels when they died?

If your test levels were good, another possibility is poisoning from some environmental chemical. Here's a great article on the subject:
https://www.practicalfishkeeping.co.uk/features/articles/2016/12/13/toxic-shock-the-everyday-chemicals-that-can-kill-your-fish
 
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ccmman

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Tank is only about a year old. The filter is an Aqueon QuietFlow 30, which is rated to work with a 30-45 gallon tank. The ammonia/nitrate levels tested low at the store ... "fine," "perfect." I had it tested twice. I don't think we introduced any household chemicals or anything like that into the system. I usually change the filter once per month, so that's why I changed it. Too often? Prior to this last filter, I seemed to have a problem with green algae, but that has been under control for a few weeks. How often should the filter be replaced?
 

InsanityShard

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You need to clean the filter in tank water, not change it. Only change it if the sponge starts deteriorating or something serious. You also need to get filters larger than their rating, because they only hold so much bacteria and only so much water passed through. For example I have one that turns over 800l per hour in a 40 liter tank, while the one that does 200 liters per hour just isn't enough... If you are low on oxygen, you could try adding an air stone. You can't clean the filters in anything but a bucket of old tank water (from BEFORE the water change) because the chlorine kills beneificial bacteria. You also cannot let the sponges or other media stay in the air for more then about 30 seconds or you start losing bacteria, they need water. I think something went too high, test strips, which most stores use, are considered very unreliable. Unless those are 0 with a max of .20ppm Nitrates the tank is not fully cycled and will harm any fish.
 

SSJ

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I've been there....i understand your frustration. here is what i did...rushed to the nearest pet shop...look for the oldest tank he has...get some water form that tank and shift ur fish immidietly into it...in a seperate tank while we figure out what wrong with the main tank. trust me..this saved lot of my fish
 

BobNJerry

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InsanityShard said:
You need to clean the filter in tank water, not change it. Only change it if the sponge starts deteriorating or something serious. You also need to get filters larger than their rating, because they only hold so much bacteria and only so much water passed through. For example I have one that turns over 800l per hour in a 40 liter tank, while the one that does 200 liters per hour just isn't enough... If you are low on oxygen, you could try adding an air stone. You can't clean the filters in anything but a bucket of old tank water (from BEFORE the water change) because the chlorine kills beneificial bacteria. You also cannot let the sponges or other media stay in the air for more then about 30 seconds or you start losing bacteria, they need water. I think something went too high, test strips, which most stores use, are considered very unreliable. Unless those are 0 with a max of .20ppm Nitrates the tank is not fully cycled and will harm any fish.
the filter the OP has is cartridges and they need to be changed or they fall apart- they also have charcoal in them and if charcoal is old it will release the toxins instead of filter them out of the water. The best thing to do is put a new one in when the old is still in there for a few days so it can pick up the BB from the old cartridge.

do you know what your PH is? y
 

Plantsmaketanks

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ccmman said:
Hello,

We have a 35 gallon tank. The last group died off slowly. Nothing out of the ordinary. We cleaned the tank, out in a new filter, and bought 12 new fish. All died in matter of days. It seemed like they were gasping for air at the top of the aquarium. Our home water test beforehand didn’t yield anything out of the ordinary. After the fish died, we replaced about 50% of the water. Test at Petsmart looked good ... twice. We got a smaller group of fish. Things didn’t look good again (fish at surface apparently gasping), so I added stress-zyme. It seemed to help, but not for 3 of the smaller fish. The three larger ones hanging on.

The water heat is about 78 and the sole plant I bought a week ago looks to be in tough shape. I also slacked on water changing when we were down to one fish prior to the 50% water change. From what I’ve read, my gut is we are low on oxygen, but It doesn’t show up in the water test and I don’t know why we’d be low.

Thoughts?
If you think it is low oxygen, in early days putting loads of bubbles via an air pump was thought to be the key. In my set ups I position the filter so It creates enough surface agitation to create transference of gases, yet also pushes the oxygen created by this to the lower level of the aquarium. I have heard that fish do die of suffocation in the lower level of aquaria due to lack of oxygen at this level. But if all areas unsure if oxygen the culprit.
 

OneLittleBubble

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It could either be the oxygen levels are not enough to support the fish or you have a parasitic problem like a gill fluke.
 

Mick Frost

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I would advocate for a sponge filter. If you have the majority of your biological filtration somewhere other than the Aqueon cartridge, you can replace it whenever that stupid light comes on without consequence. Clean it in old tank water with a squeeze and a light rub when you do your WC, but not the same week you replace a cartridge.
I use sponge filters almost exclusively, and I'll clean them at most once a month.
As for the main issue, did you watch the test being done in store? The Nitrite test can be easy to screw up if they're lazy or inexperienced, and Nitrite Toxicity is the most likely culprit here. Not to mention the effect of artificial light on the color, or poor training leading to the thought that 1ppm is "perfect" or "fine".
That's if it was a real test, and not a strip.
Sorry for your loss.
 
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