Sick Cory?

[nigelnorris]

Hi, thanks for coming to look for me. My first ever tank, and a week ago I got my first ever fish, half a dozen panda corys. Five of the six have settled in nicely, a bit timid but they're spending less time hiding and glass surfing and more time just ambling along and rooting about, they don't look in any way stressed. They're all quite small, I'd say about an inch and a quarter. The sixth is very different, spends all of his/her time, I mean hours on end, doing circles around the glass panes, 3 inch circles over and over again on the same bits of glass. It looks like he's rubbing his head against the glass as he goes.

The tank is properly cycled, zero ammonia / nitrites, <20 nitrates, I only have test strips but they're consistently well within the green zones for hardness, ph a bit below 7. Got wood, it's planted, lots of hiding places.

He managed to stay still long enough for me to get the photo attached, and I can see that there's a rough patch high up where to my eye there should be plates, and a red patch just below his eye. Haven't seen the other side. Fingers crossed I'm over concerned but surely his behaviour must be abnormal?

 

[Colin_T]

video of the fish doing circles?
upload video to youtube, then copy & paste link here

 

[nigelnorris]

Thanks Colin. Never even recorded a video before let alone uploaded anything to youtube so I've learned something already. Here's hoping.

Stopping off at the plants is a red herring I think, he can go for ages round and round across and up and down the front panel of the tank non-stop.

 

[Colin_T]

the video is set to private. go into YouTube settings and make it available to general public

 

[nigelnorris]

Thanks, should be good to go now.

 

[nigelnorris]

I can't believe what I'm about to say, but it occurred to me that the bit filmed above he was circling in the stream of the filter output. So I turned it off and, like a switch, he just stopped doing it. The front panel I mentioned above also catches the flow from the filter out.

7 days straight killing himself fighting against the current, when there are plenty of calm places to go. Got to be more to it than just playing in the stream surely?

 

[Byron]

I think I know what is occurring here. Two things. First, I would consider this one cory to be a bit stressed, which is not surprising as you have only had them a week. Some cories do not like changing their environment at all, and react for days, even weeks, while others seem much quicker to settle in. This behaviour is very common in such circumstances. This is natural, and I would not do anything, but don't do anything to add to the stress.

Second point to mention is that this cory species occurs in the higher Andes streams in Peru, where the water is cooler and flows faster than many lower watercourses. I have had C. panda in my tanks for many years, along with 12 or more other species, and the pandas have always been much more active in filter streams. You are correct in saying that they need to be able to get out of this if they want, and it seems there are, so not a problem here either.

You might consider getting a few more. All cories are highly social, and groups of 10+ is well advised. You have six pandas, so you could get another five or six, or you can get a different species in a group of five or six. But I would have more cories than six, it really does make a difference to the individual fish.

 

[nigelnorris]

Ok Byron, that's helped a lot, many thanks for your input! It's not a big tank, only 30 gallons with less than a three square foot footprint, not sure if it would stand > 10 corys? I'll get at least a couple more next time I'm in the shop. Maybe increase numbers gradually once I have other fish in there too..

 

[Byron]

Ok Byron, that's helped a lot, many thanks for your input! It's not a big tank, only 30 gallons with less than a three square foot footprint, not sure if it would stand > 10 corys? I'll get at least a couple more next time I'm in the shop. Maybe increase numbers gradually once I have other fish in there too..

You have space. The thing to remember is that the number of the species (this applies to all shoaling/schooling fish, not just cories) is extremely important for the well-being and health of the fish. Studies have proven that a group of five displayed serious stress-related issues that a group of ten do not. Having a larger group must be the overriding concern. And you have space in a 30g, which I will take to likely be 30 inches/75cm in length. Cories love browsing all surfaces, even the leaves of floating plants at the surface. They do not swim actively in "relays" so the surface area which includes the substrate, decor, and plant leaves is what matters to them, not area of the tank floor.

And, acquire all the intended cories at the same time. This too applies to all shoaling/schooling species. The more there are together going into the tank, the quicker they will settle down, and that means significantly less stress and less chance of ich which is caused by stress. So get all five or six, not one or two or three.

 

[nigelnorris]

Okey, more it is then! Yes, taking the plants and hardscape into account there's certainly more than the bare three square feet. Thanks.

 

[nigelnorris]

Not so sure now. Every since that last post I've been reading and can't find anything at all in the way of useful research. There is one paper that says, a bit like what you said, that ten are less stressed than five. But that's not applicable here because they only tested 5 or ten. I'd bet that if they'd done five and eight, or ten and twenty, the results would have been the same; that is, bigger shoals implies less stress. But if they'd done the latter we wouldn't all be upgrading our tanks to include 20+ corys.

I'm going to upgrade from 6, but so far I'm taking the number ten with a pinch of salt.

The good news is that the mental one is starting to calm down now, and spending time with the others looks to be helping him/her.

 

[Byron]

Not so sure now. Every since that last post I've been reading and can't find anything at all in the way of useful research. There is one paper that says, a bit like what you said, that ten are less stressed than five. But that's not applicable here because they only tested 5 or ten. I'd bet that if they'd done five and eight, or ten and twenty, the results would have been the same; that is, bigger shoals implies less stress. But if they'd done the latter we wouldn't all be upgrading our tanks to include 20+ corys.

I'm going to upgrade from 6, but so far I'm taking the number ten with a pinch of salt.

The good news is that the mental one is starting to calm down now, and spending time with the others looks to be helping him/her.

I do not argue scientific fact. Here is a link to the paper, which is one of the best, but I have seen others.

And you will not find one reliable source disputing what I posted. This thinking is more recent, as scientific evidence becomes more prevalent on topics like this one that went un-studied until more recently. Shoaling/schooling fish like herd animals need a decent-sized group, and the fish/animals will be stressed the fewer there are. For many years "six" was considered to be minimum, we now know different. We learn as the science progresses.

https://www.academia.edu/download/50054534/The_effect_of_group_size_on_the_behaviou20161102-6716-1m0ezpq.pdf

 

[nigelnorris]

Thanks for that reference Byron, but the link's broken.

If it's "The effect of group size on the behaviour and welfare of four fish species commonly kept in home aquaria", I've found it elsewhere so no worries.

 

[Byron]

Thanks for that reference Byron, but the link's broken.

If it's "The effect of group size on the behaviour and welfare of four fish species commonly kept in home aquaria", I've found it elsewhere so no worries.

Yes so it is. You can track it down. If you use Google Scholar and enter some keywords like shoaling/fish etc you will find several. The primary I use is
"The effect of group size on the behaviour and welfare of four fish species commonly kept in home aquaria, by Amelia Saxby, Leoni Adams, Donna Snellgrove, Rod W. Wilson, and Katherine A. Sloman, Applied Animal Behaviour Science 125 (2010), pp. 195–205.

 

[nigelnorris]

Too harshly worded so I've edited down to this.

All of the trials were done in 10 litre tanks. Amongst other species 10 angel fish in one 10L tank. There must be many stresses caused by the tank size alone that don't apply to our home aquariums. Nothing coming from that could possibly relate even to my small 140l tank.

Secondly, as I said above, all they did was compare 1, 2, 5, and 10 shoal sizes. And the more the merrier, no surprise. but that doesn't mean that ten is in any way ideal, it's just the biggest number they chose.