View Full Version : My Corydoras personality and behavior changed radically after 5 months-what happened?

09-13-2020, 04:31 PM
Hi Everyone, This is my first post and this is my first membership in an aquatic community.

My husband got a 37 gallons tank back in January of this year. He has three Corydoras, three Congo Tetras, 6 hyphessobrycon HY511 (Candy Cane Tetras), 3 Harlequin Rasboras, 8 Cherry Barbs, 1 Dwarf Gourami. That's 24 fish. He got them all from a company in Wisconsin that mailed them, and it took longer than it was supposed to. There were at least 6 Rasbora and more Barbs but they died shortly after arrival. Also, two of the Congo Tetras (male) have gotten really big. And the Gourami came by himself with no partner. This is not how we would have planned the tank if we knew better at the time. There aren't enough of the smaller fish and the tank isn't big enough to start adding more now.

When we first got the fish, the Corydoras, which are healthy and hearty and have grown a bit were really friendly and comfortable. They were very active and played with each other, diving and swimming together and eating from the bottom of the tank like crazy. They vacuumed the gravel from one side of the tank to the other. We always had a lot of natural plants and when some plants didn't make it my husband replaced them with others, they have become thick, providing a lot of cover on both sides of the tank and in the middle there are shorter plants. There are plenty of natural rocks, with niches to explore. There are short, tall, thick, thin, large and small rocks Ė a good variety, with natural colors.

At the beginning of June when my husband first got some thick plants that came all twisted together and took a long time to spread out. The Corydoras immediately claimed that area on the right side of the tank away from the window and hid. The Candy Cane Tetras also like it there are always a few hanging out close to the bottom. The Corydoras and the Candy Canes seem to ignore each other. The Corydoras stay farther back. The Candy Cane fish like it there I think because they are always spawning, and the two males and 4 females use it to lay and fertilize eggs which the Cherry Barbs always immediately eat.

It has gotten so I never see the Corydoras anymore. I wouldn't know they were alive if I didn't spend a lot of time peeking in trying to find them in the back, they are always sleeping or just lying there in which case they see me and get startled and run away. It is impossible not to spook them if I am looking for them on the bottom. If they ever come out to feed in the front of the tank now, they are skittish and run away so fast from the slightest movement even far away from the tank. The minute a person even comes into the room which is big they move so fast to hide they startle the other fish. My husband sits there are if they come out, he canít move or they will hide again. They do not like to be seen by people and they ignore the other fish but do not stay in the open ever.
They were the opposite until June when we got thicker plants. I could stand in front of the tank and they would look at me and then go back to hanging upside while vacuuming the bottom of the tank. They donít play together anymore. They do not swim around or go to the top anymore which I know is only if they need oxygen so maybe that's a good thing. They look well fed and healthy on the rare occasion I catch a glimpse of any of them. Only one, the biggest, comes to the front of the tank occasionally when I feed them, but he immediately hides again. The two others hang back. They all do not seem happy to me, hiding away and not being part of the community of the tank anymore. They are like ghosts, or invisible. They eat whatever food falls to the back of the tank unseen by us and they do not seem to like being seen.
I have watched and watched to see if they are harassed or injured by the other fish. The other fish ignore them and maybe would swim close by, all the fish except the Rasboras go toward the bottom of the tank at least sometimes.

Is it possible that the fish grew up and became mature and are now acting the way they are supposed to? Is it that now they have heavy plant cover which is what they always wanted? Or is it possible they are bullied by other fish when we aren't looking, like at night? They do not seem to be injured in anyway, but it is getting to the point where we hardly ever see them anymore at all.

What do you guys think?

09-13-2020, 11:54 PM
Cory's are social and do best (will be more active and secure) in groups of at least 6, better 8+. Maybe you can upgrade your tank to bump up population in your tank as many fish you have need bigger groupings to also be their best.

Lol if you're in the northern IL area, we have some tanks going dirt cheap...40 breeder for $40 or a 75 gallon for $50.:hmm3grin2orange:

09-14-2020, 03:08 AM
I don't think there is a problem with your cories. I have a 40g tank with 6 Cory Schwartzi and 3 Cory Caudimaculatus. They've been in my tank 4-5 years and I also don't see them very often. Occasionally after a water change I might see them a little more active for a short time, then they are mostly in the back of the tank, or in some nooks under the driftwood, just hanging out. If they are out feeding, they will run when I'm near the tank. I have Candy Cane tetras and Diamond Tetras in with them and nobody is bothered by anybody.

I have 6 dwarf cories in another tank and they hide out in a very thick group of crypts I have and act the same way as those above. But in a 3rd tank, I have a single, very old (gotta be pushing 9 or 10 yrs) sterbai cory remaining from a group of 3 with a bunch of endler guppies and a few pencilfish. This one guy is not bothered by anything even if I'm near the tank.

09-14-2020, 12:18 PM
Welcome to the AC.

I agree with adding more corys, they do better in larger groups..as do the harley and the congos...what kind of cory are they?....also, most corys tend to be more active at night than during the day.

And FYI, not only do the congos need to be in a larger group, but they grow too big for a tank that size...

09-15-2020, 08:08 PM
Mmmmm weird.
Could definitely be that the mature fish need more company of their own to feel secure.

What are you feeding them ?