Corydoras Keep Surfacing, Weird Behavior

[Katty]

First off, yes, I know corydoras will shoot up to the surface and swallow air sometimes. I have had these guys for 2+ years and can tell when they are doing that. However, this is a little different.

Tonight when I was doing my weekly water change I noticed one (well I think it was only one but they all look the same) of my 3 albino corydoras kept slowly swimming up to the surface, touching the tip of his nose to the surface, and wagging his tail all while he was doing this. He'd stay in this position sort of nosing the surface for maybe 5 seconds. Then, he'd look like he'd "changed his mind" and turn back around and meander back downward. Well, I turned off the filter to clean so I had thought that maybe there was just low oxygen in the tank or something and he was trying to get more air. I top off the tank, turn the filter back on, and he keeps periodically doing this. Then I check up on the tank a few minutes later, and it seems like all of my 3 albinos are doing this, and seem to always swim up to the corner or rim of the tank and kind of hover with their noses touching the surface. This does not look at all like when they "get air", you know, shoot up to the surface and shoot back down again. The one bronze cory I have (which is younger than the others, less than a year old) I have not seen do this weird behavior, yet.

Also a few months ago when I added the bronze corydora, there was another bronze corydora as well. As soon as I got it home it swam very very very slowly and when it went to the surface it would do it very very slowly, sort of like what my albinos are doing now. I should have returned it to the store but I figured it was just a runt or something and put it in with the rest. After a month it just died for no reason. So I'm kind of worried maybe it gave the others something.?

There are tetras and a cichlid, and 2 otos that I added a week ago, none of which appear to be acting off at all.

What's going on?

 

[Caprichoso]

I would check for ammonia in your tank first, just to make sure all is well in that department. Also, has the water temperature changed at all? Even a degree can make them act differently. That being said, I have seen my green corydoras do that same thing on occasion but I couldn't find anything wrong with the water. I did have a Sterba Cory who did the same thing though this year and he ended up dying. All you can really do is make sure the water is good. Some of these things are really frustrating and you end up feeling a bit helpless. Good luck!

 

[Harlequins]

Has you say all corys dive up to the top now & then,but if they are doing it more often that not and staying there then it may be lack of oxygen or water stats may be out.

Has mentioned check you ammonia & nitrite to make sure alls well.

 

[Katty]

The water temp might have changed a couple degrees, I used cold water to replace but the one was doing that all while I was filling then the rest started after. It is frustrating! Fish cannot tell you what they are thinking.

I got up this morning and they are all just resting, one is foraging, none of that funny surface stuff. Lights are off though. Hmm maybe the water change knocked out some weird gunk in the water column. I'll test after school today.

 

[Coryologist]

Without actually observing the fish, it sounds like pre-spawning behavior, to me. That fact that a lone fish died, is probably an entirely different issue. Fish die, suddenly, without any symptoms for myriad reasons. Trying to determine the cause is an exercise in futility. - Frank