A Filter fiasco in our tank?

I'm inclined to believe along with Rocky there, that the fish probably weren't in like Olympic condition. I mean in tanks, it's not very easy to have studly perfectly healthy fish as it is. I mean you have to also consider it from the prespective that fish in the wild have an almost unlimited naturally refreshed water, and filtration really isn't an issue. Now we all as hobbyist take these fish that evolve outside of tanks, put them in a closed loop enviroment like that, I'd have to assume it's going to be detrimental to some degree.

If this were me, this is how I would approach figuring this out.

1. I'd immediately test the ammonia, and nitrite levels to see how elevated it got, and also verify the nitrates too. 2 days is fast like you said, but let's also assume in this case, it had already been like a week or so since last water change, and you already had significant nitrate build up. If it were me, I'd like to just know what the nitrate levels are in there now.

2. Verify there was no PH crash and check on the GH and KH levels too. I don't think this is a likely cause, but like a doctor does, rule everything out too. I suppose there is a possiblity, that with one filter down, should the hardness levels been weak, maybe the PH shifted vastly and rapidly? I'd verify that just to be sure.

3. Do your visual check on the temp, verify thermometor is working. Might seem very out of the way, but maybe there was a possible electrical outage that triggered the filter break down. I've seen my cannister filters be very sluggish for 15 or 20 mins when we have power outages. Really simpy thing and easy to check.

4. Assuming the air flow is working, which I'd feel it would be, you wouldn't miss something like that, what is the total or was the total tank population? What I do find odd out of that listing of dead fish, is that the Gourami is an upper level fish, and the other two, bottom feeders. Just outwardly looking at that list. I don't see aggression or fighting to be likely as the cause. What exactly did you see out of the Gourami before it passed?

5. What's the typical diet you give, just by chance. I doubt you offer feeders knowing the hazards of that, but what do the fish usually eat?

I wish I had more to offer at this point, it is very late here however so I'll check back in on this one. It is possible, that ammonia did do this though. Let's just figure, half your bio filter down, if your bacteria was stable to handle the current load, and then got cut in half, it's not going to be able to bloom out enough, so there will be a build up. Now, just say you have a PH of like 7.8 or higher in there, that build up is going to cause a large amount of damage just because of the PH factor. In many cases, in PH's over 8, it's pretty much lethal. I'll check back in later or tomorrow.

Well damn, I don't see anything that clearly stands out. The loss of color in the Gourami that died does seem to be some sort of indicator. I mean, if one of the stock just up and died outright, like a person having a massive corenary, you kind of have to investigate, so the loss of color is making me think, it's a clue to something that was going wrong or what did go wrong.

Other then that, when you would feed them, there wasn't anyone showing a lack of appetite right? I'm going to spend some time looking over loss of color in a fish, and what are likely causes.

The only things I've been able to see point to things that don't seem to make much sense, unless you tie it back into fish being weak already. Most common factor of loss of color I found was Neon Tetra Disease, but that you would have seen long before. Other is parasitic infections, which could be a case if you maybe didn't quarenntine long enough. Possibly this might be a fungus, but I'd suspect you'd have seen that on other fish. I'm sorry I can't seem to narrow this down any further.

I follow this question up with Carl S, my manager at Everything Aquatic, and he gave me a few links that I think will help. Feel free also to stop over at our site.

http://www.americanaquariumproducts.com/Basic_Aqua...

http://www.americanaquariumproducts.com/AquariumKH...

http://www.americanaquariumproducts.com/Aquarium_F...

I've personally found the articles on KH and electrolyte balance have helped me tremendously.

You'd be amazed how fast a seemingly minor aquarium problem can have this kind of effect. My guess is that the dead fish were already a bit weak and this incident was more than they could handle. If the other fish have survived this long they'll probably be okay, but watch for any more dead ones. If they stay in the tank very long it would make things worse. The tank will probably have a small ammonia spike soon, so test the water frequently and do water changes if needed. In a week or two everything should be back to normal. By the way, tell your sister not to mess with the tank anymore.

It doesn't seem likely that is what killed the fish, but a dead fish will kill the other ones from the bacteria, I moved a fish into another bowl to save it, it lasted a week and then died. Good luck solving it.