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Disaster

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So I’m having trouble making sense of what happened. Yesterday I did a 50% water change on my 75 gal tanganyikan tank, as I do twice a week. The tank is well established and has been running for nearly three years. 

I finished filling the tank and left to pickup my son at preschool. I came home to realize that I had forgotten to turn the heater and filter back on. I was gone less than an hour and the air stone was on the whole time. The temp was at 76 degrees F ( only slightly cooler than I keep it at 78-79 degrees). I turned on the heater and filter and thought everything was ok. It was then that I noticed one of my julidichromis transcriptus was dead and my synodontis multipuncatus was floating vertically. The syno would swim around a bit but it looked like it was having swim bladder issues and it would always end up in this vertical position. 

I immediately tested the water and started to do another 60 to 70% water change. The tests didn’t show anything out of the ordinary. Ph 7.8 , ammonia 0, nitrite 0, and nitrate about 5-10 ppm. I also tested the water out of the tap and there were zeros for all and ph 7.8. 

As I was siphoning I noticed that some of my synodontis petricolas were starting to display the same symptoms as my multipuncatus was and some more of the Julie’s weren’t  looking so hot. 

Over the next couple of hours I lost a total of four petricolas, three julidichromis’, and the multipuncatus. After that I had to leave and pick my wife up from work. I fully expected more casualties when I returned but there were no more. My remaining two petricolas were swimming around as usuall. The three remaining julies were not looking great but they were alive. My altolamprologus were all seemingly fine they were hiding in the rocks as they do during every water change but their colours and patterns did not appear as if they were too stressed. I have 3 yellow calvus, 1 black calvus and 1 gold head compressiceps. 

So far this morning all the remaining fish look healthy and are not behaving abnormally. I also have a 150 gal with peacocks and haps that’s due for its water change but I’m hesitant to do it yet until I find out what’s going on. I have heard of the city adding something to the water at certain times that could be detrimental but I’ve never had this happen before. I’m in silver springs in NW Calgary. 

Ive also considered that it could’ve been trapped gasses in the substrate but I have Malaysian trumpet snails and I regularly stir up the sand to avoid that sort of situation. Also the fact that only half of the fish in the tank seemed to be affected makes me think that this is not the case. 

Can anyone offer an explanation? I’m at a loss. 

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Did you forget the dechlorinator perhaps. Also some fishes from lake tang do not like large water changes.

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I agree with Geleen on this one. Occams Razor should probably be used and I think that forgetting to add de-chlorinator with a large water change could be the best explanation. Hydrogen sulfide production in anaerobic zones can happen, but if you regularly disturb your substrate while doing your twice-weekly water changes you can probably rule that out.

Sorry about the disaster, but it sounds like your taking great care of your fish. We all forget simple things on occasion and it can lead to sad outcomes. The exception does not prove the rule ;-)

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Since you have been doing this twice a week for 3 years I think it more plausible that this unusual mishap is linked to the unusual event of forgetting to switch heater and pump back on. I would say there is zero chance that the little temperature dip is an issue but leaving the pump off for an hour will leave the filter in an anaerobic state for a good amount of time and when bacteria don't have oxygen they start to use nitrate, sulfate etc instead and create a whole soup of anaerobic products including hydrogen sulfide. If the filter is small relative to the tank volume I would not have expected the consequences to be that dramatic but IMO releasing the anaerobic soup into your tank when you switched the pump back on is the most likely cause for your disaster. In future, redirect the pump outlet into a large bucket and flush out a few filter volumes worth of water when you switch the pump back on. After that it should be good to operate again.

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Biodives I was unaware that aerobic bacteria can switch to sulfate/nitrate reduction and swap oxygen for sulfates/nitrates as a terminal electron acceptor. Could you please post a link to this because I have never come across this before. It should be scintillating read.

Thank you

Andrew

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 Biodives thanks for the input it’s definitely something to consider moving forward. While I can see how that could have contributed to the situation, the fact that I already had one casualty and multiple fish in distress before I turned the filter back on tells me that my mistake happened earlier. I spoke with someone with the city this morning and was informed that aside from a slightly higher mineral content and (due to the colder temperatures causing the chlorine to take longer to dissipate) slightly higher chlorine consentration, that there should be no other differences in the water supplied from the city. 

So I have concluded that, despite my usual diligence, I must have forgotten to treat the incoming water. I didn’t want to admit that this was a possibility at first but I think that it’s the most logical explanation. 

As embarrassing as that is I have to look on the bright side. I didn’t wipe out all the fish. And now I have room in the tank for new fish. Haha fml

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On 13/12/2017 at 9:45 AM, biodives said:

Since you have been doing this twice a week for 3 years I think it more plausible that this unusual mishap is linked to the unusual event of forgetting to switch heater and pump back on. I would say there is zero chance that the little temperature dip is an issue but leaving the pump off for an hour will leave the filter in an anaerobic state for a good amount of time and when bacteria don't have oxygen they start to use nitrate, sulfate etc instead and create a whole soup of anaerobic products including hydrogen sulfide. If the filter is small relative to the tank volume I would not have expected the consequences to be that dramatic but IMO releasing the anaerobic soup into your tank when you switched the pump back on is the most likely cause for your disaster. In future, redirect the pump outlet into a large bucket and flush out a few filter volumes worth of water when you switch the pump back on. After that it should be good to operate again.

Thanks so much for posting this. I read this thread yesterday and went home to my goldfish at the top of the tank. After doing a water change the night before and all fish were normal, I did forget to plug the filter back in for about 30 min plus the time it was off while above the water line when empty/filling so at least an hour.. Nitrates through the roof. I will be sure to be more mindful of my timing on this or clean the filter at the same time to prevent so much new waste from entering the water again. 

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On 12/13/2017 at 9:43 PM, FunkSolid said:

Biodives I was unaware that aerobic bacteria can switch to sulfate/nitrate reduction and swap oxygen for sulfates/nitrates as a terminal electron acceptor. Could you please post a link to this because I have never come across this before. It should be scintillating read.

Thank you

Andrew

Some bacteria are either strictly aerobic or strictly anaerobic but facultative anaerobic bacteria, E. coli being the best known example, prefer to use oxygen but under anoxic conditions they switch to use nitrate, sulfate, fumarate or other terminal electron acceptors (https://www.sciencedirect.com/science/article/pii/S0005272897000340). Ammonia oxidation in our filters is aerobic but there are bacteria that can do so anaerobically (ANaerobic AMMonium OXidation ANAMMOX bacteria) and even some Nitromonas-like species have been found to be able to do this (http://www.sciencedirect.com/science/article/pii/S0168649601002082). Filters don't only contain ammonia-oxidizing bacteria so there may be other facultative anaerobic species that can produce anaerobic metabolites of various kinds.

I certainly have switched on filters that had been switched off for a while without ill consequences but most of my tanks have no filter or a very small one relative to tank size. But if I decide to do a filter clean prior to switching it back on it has a distinct unpleasant smell. So collecting a few filter-volumes worth of water in a bucket after switching on an anoxic filter seems like a good precaution.

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