Cory catfish not schooling and some never come out

[Inessa]

Hello everyone,
So I'm new to this all 🙂 I have a 55 gal with nano schooling fish (neon tetras, celestial danios etc) and I had no bottom fish, and I wanted Corys , so I went to pet shop and bought 3 Corys that were left (I knew I need 6 of the same kind but I thought I'd come back and buy the rest , as they keep reordering them). At home 2 Corys started exploring and being active , 3rd hide away so I did not see it ever since . I thought maybe it's because the school is not big enough , but guess what, they did not have the same kind anymore in the pet store for few weeks so I used Google lens to determine which kind I already have and Google said it's Cory Agassizi, so ordered 3 more online , - which turned out to be similar looking , but different. Later the Petco manager said my 1st batch was Cory Punctatus. The new batch of 3 Agassizi had the same behavior problem - one fish is active, 2 disappeared and never showed up again (I have a heavily planted tank with lots of hideouts). So as for now, I see only 3 fish viable :2 Punctatus and 1 Agassizi swim together happily, eat and dig- whereabouts of the rest is unknown (they are not dead, all the tests are normal , plus I saw them sneaking around when I moved the rocks and everything to clean and make sure they are not dead). Will they ever find each other ? What happens to the Corys that never come out, are they gonna die of stress and loneliness ? Looking at how close these two kinds are, can I hope they will school together- or what should I do? (Adding 6 more , 3 of each kind - is not really an option because by now I already have 10 happy pandas too , so it's 16 Corys for 55 gal) it's been only a couple of weeks, but I'm worried so I would appreciate your advise. Thank you!

[Aiken Drum]

Are the corys hiding just when you are near the tank, or do they come out when you on the other side of the room?

While corys arent strictly nocturnal, they are often more active at night. So just because you dont see them swimming about, feeding and exploring it doesnt mean they arent doing so when you arent around.

What you say is a bit confusing. You say you had no bottom fish so got 3 corys, and then another 3 corys. But then you say you already had 10 pandas, so you did have bottom fish? Perhaps the larger group of panda corys are whats causing some of these new fish to not settle.

Personally rehome the 6 newcomers and stick with the panda corys rather than have 3 different species of cory some of which dont seem happy.

[Inessa]

Thank you for answer. Sorry for confusion.. I got 3 corys with dots first which I thought were Agassizi , - and therefore I ordered 3 more Agassizis online since they did not have any more in the store available . While waiting for that delivery which took almost 2 weeks I bought and added 10 little pandas because I wanted them regardless and had space in my tank (I did not expect them to school with spotted ones anyways ). Once my Agassizi arrived , I realized they look different from the spotted ones I already have , so I went back to the store and they told me that my first batch was Punctatus, not Agassizis , but it's not a big deal since the difference is so minor and they will school together anyways. And it's true, 2 Punctatus and 1 Agassizi school ok, and the rest - 1 Punctatus and 2 Agassizi are just never coming out , not single , - not in a group -not ever. When you say re-homing, sounds easy , but realistically I don't see that possibility. Plus I like them and would try to keep them all, so I'm trying to figure out a solution

[Inessa]

Ok I will try to word my question differently. Currently I have in 55 gal:
8 neon tetras
5 Celebes rainbow
3 platies
6 Galaxy rasbora
Cherry shrimp, snails
10 panda Cory
and as a result of mistake -it was supposed to be a shool of 6 Corys of the same kind but I ended up with :
3 Agassizi Cory and
3 punctuatos Cory - only 3 mixed individuals of the group of those 6 seem to be happy.
Options 1) Do I still have room to add 1 or 2 or 3 of each Agassizi /and punctuatus ? Should I consider that at all? Or I will end up adding more, overloading my tank and the ones that are hiding will still keep hiding?? 2) should I wait to see if the ones I have will come out and join the existing group ? How long is normal3) ..???...

[Andy Sager]

The first thing you need to know is that not all species of corydora catfish will school together or even tolerate each other. So far, it sounds like you got lucky that any of the punctatus and agassizi want to be with each other. There can be a number of reasons why your other Punctos and Agis are hiding. They could be unhealthy. They could be scared because of the new tank surroundings. They could be getting picked on by the pandas. They could just be trying to adjust to their new home. ....As long as you see them eating, they are probably just trying to adjust and I wouldn't worry. As for how long to wait to see if these things change, there is no answer. Not all fish are the same to each other or to other species. If you see the Pandas or other fish harassing them, then the time limit is up and the cories should be removed from the aquarium.

As Aiken suggested, I would seriously consider rehoming the Punctatus and agassizis and stick with just the pandas rather than add more of either to make a bigger school. There is such a thing as too many bottom feeders.

[ColdKoi]

I also have 2 different flavours of Cory and similar findings.

Generally they stick together in species specific schools, but there’s times that they all hang out together. Generally it seems my pandas are more social, I see them out more often during the day whereas the peppers tend to hide out in the shadows. In either case, they’re both a lot more active after the lights are out

I guess it’s more or less just normal behaviour

[Colin_T]

What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website (Water Analysis Report) or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

Celebes rainbowfish come from hard water with a slightly alkaline pH.
Neon teras come from soft water with a low pH.
If the GH and pH are too high, the neons and Corydoras won't do as well. If the GH and pH are low, the Celebes rainbows won't do well. Ideally you want 2 tanks, one for the platies and Celebes. And a second tank for the tetras, danios (galaxy rasboras) and Cories. Then try to make the water suitable for the respective species.

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As for the Corydoras not swimming during the day, these fish are normally nocturnal and don't spend a lot of time out in the open when it is light. Some settle down over time and will come out and about. Others remain hidden and only venture out after dark. Clean water, lots of plants and a bit of frozen or live food can usually entice most out into the open, albeit for a few minutes before they hide again.

Re: schooling. They are more likely to group up when in large numbers (20+) or if frightened by a larger predator. In an aquarium with no predators, the fish tend to be more relaxed and spend less time staying in a group. This is typical of Corydoras, tetras, danios and rainbowfish. Increasing the number of each species to 12 or more might encourage them to move in a tighter group, but might not if nothing is threatening them. Your tank is probably big enough for a few more tetras and danios but you need to find out what the GH and pH are so you don't shorten the lives of the fish.

[Joe_D]

Cory are not really schooling fish. However, they will tend to rest and feed together on the bottom

[Inessa]

Guys thank you for your replies! I understand it's a sensitive matter whether certain fish is happy in a community tank, - but great news, 5 of my 6 larger Corys (speckled /Agassizi) already started to be schooling and eating together, hopefully the last one will join once he gets more comfortable. Honestly, they look so similar , - one is just exactly an interbreed, I can't even tell which school he is from . 10 little pandas are also having a blast In their own group too , they are tiny little bees , the most peaceful fish ever, - just like shrimp or snails not picking on anyone ever . Thank you everyone who replied 🫶 best of luck with your projects .

[Inessa]

Thank you !.. exactly that, as they are actually the biggest fish in the tank lol so there is nothing to be frightened of really. And I am not planning to introduce any aggressors
Plus they have their own Cory house/cave. But I see them making a mixed group now- that makes me more comfortable