IMPORTANT lesson about mysterious fish deaths -- have never read this anywhere - GTA Aquaria Forum - Aquarium Fish & Plants serving the Greater Toronto Area.
GTA Aquaria Forum - Aquarium Fish & Plants serving the Greater Toronto Area.

Go Back   GTA Aquaria Forum - Aquarium Fish & Plants serving the Greater Toronto Area. > FRESHWATER > Beginner's Circle
Register FAQ Members List Calendar Advertise Search Today's Posts Mark Forums Read Advertise

Beginner's Circle This forum is dedicated to helping people new to the hobby. If you need help, this is your starting point.

Thread Tools Search this Thread Display Modes
Old 10-17-2016, 12:30 PM   #1
Junior Member
Join Date: Jun 2016
Location: Toronto
Posts: 34
Feedback Score: (0)
nature has a spectacular aura about
Default IMPORTANT lesson about mysterious fish deaths -- have never read this anywhere

SUCCINCTLY, the lesson is:

If fish are dying but parameters seem fine, RUN WATER TESTS WITH SAMPLES FROM THE PARTS OF THE TANK FARTHEST FROM YOUR FILTER. (I used a dropper to suck up the water from a specific spot.)


After over six months of successfully keeping my ember tetras, in tanks of two sizes, I recently had a wave of deaths ... not all of them, but at least six on two different occasions, in my 29 gallon tank. After the first wave I did a major water change, which seemed to stop the deaths for about a week.

Ammonia and Nitrite were zero when I tested and I have been using Algone for nitrate so was pretty sure that was not the issue (API nitrate tests have been sold out!)

After the second wave of deaths I realised that my Kubotai Rasboras, which stay in the top four inches of the tank, and which are supposed to be very susceptible to water quality, were not affected. I did not however notice any odd symptoms in the tetras except right before they died, so I was really mystified as one of my fish died from a disease a while back and it was obvious and took a while.

A few days before the problem I had added my most mild-mannered betta to the tank (he's been great! No problems with either fish or shrimp). I have always had two filters going in the tank, one a large sponge filter, the other an internal filter which gave good water circulation. I took the internal filter out and replaced with a HOB filter (but used the sponge from the internal) because I know from experience that the Betta's tail can get stuck on the intake of the internal.

During the second wave of deaths, I thought about the rasboras being okay, and realised that the water flow had been diminished because of the changes I made to the filters to protect the betta. For aesthetic reasons both filters are in one corner of the tank. I decided to test at the very bottom corner diagonally farthest from the filters. When I did I discovered that ammonia was still zero but nitrite was quite high. It actually makes sense that if your filtration is inadequate you may have different values throughout a tank. However I have never read about this anywhere.

Thankfully once I realised this I looked more closely and found a few of the tetras did look a little off. I took them out immediately and put them into fresh water. It took a while but all three recovered and could be returned to the tank. Unfortunately between the two waves I did lose about seven tetras -- almost half of my total.

To fix the problem I made an adjustment to the HOB to increase the flow a bit. I also put a third, small sponge filter in the corner where the reading was bad. No problems since then.

Last edited by nature; 10-17-2016 at 01:10 PM..
nature is offline   Reply With Quote
Sponsored Links
Old 01-06-2019, 01:34 AM   #2
Plantedtank Noob
Join Date: Mar 2012
Location: Mississauga
Posts: 270
Feedback Score: (6)
vraev is on a distinguished road

Thanks for sharing. I just got a poppy style lily pipe and noticed my fish breathing a bit more heavily at the back corner and was just wondering if this sort of scenario is possible. I have an Eheim skimmer which I’ll position at the opposite side to flow water to that spot tomorrow.
vraev is offline   Reply With Quote
Old 03-28-2019, 10:02 PM   #3
Devoted Member
Join Date: Mar 2012
Location: Mississauga, Ont. Canada
Posts: 2,983
Feedback Score: (70)
Fishfur is a glorious beacon of light

I would think this kind of issue might be preventable just by adding some circulation to the tank, by way of a separate pump.

Granted, a Betta won't appreciate too much current, but a very small pump that's not very powerful, and properly placed to address such areas, would still push water around and help to alleviate this kind of thing.
~I am willing to ship plants/stuff other than livestock, to any member, from retail stores or private sales. Also willing to pickup/deliver. Modest fee + my costs.
Please PM for details.
Fishfur is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT -4. The time now is 06:18 AM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.