Okay, so I need to tell you about the time I completely wrote off an entire group of fish and then had to eat my words… along with learning a bunch of stuff that nobody at the fish store bothered to tell me. This was maybe three years into my aquarium obsession, when I thought I knew what I was doing (spoiler alert: I absolutely did not).
I was at this local fish shop in Campbell – not the fancy one, the cramped one that smells vaguely like old water and has tanks stacked to the ceiling. Anyway, I’m walking around looking for something interesting for my 20-gallon community tank, and there’s this whole wall of these dumpy-looking bottom fish. Little mustached catfish just sitting around on the substrate like tiny underwater bulldogs. The handwritten signs just said “Cory Cats – $3.99” or whatever. I literally thought “ugh, boring cleanup crew fish” and went straight to the neon tetra section instead.
Fast forward two months and my tank is developing this gross layer of uneaten food around my java ferns. My boyfriend (who knows nothing about fish but has opinions anyway) keeps asking why there’s “fish food dirt” all over the bottom. The same shop guy who sold me the tetras suggests these bronze corydoras, claiming they’ll clean up the mess and I won’t have to vacuum the substrate as much. Fine. Whatever. I bought six of them expecting aquatic roombas.
What I got was… honestly, six of the most entertaining fish I’d ever owned.
First thing they did was completely ignore the uneaten food I’d bought them to clean up. Instead, they immediately formed this little expedition group and started systematically exploring every single inch of the tank. Not randomly swimming around – I mean methodical exploration. One would stick its face deep into the substrate near a rock, and within seconds the other five would rush over like “whatcha find whatcha find whatcha find?” Their little barbels going crazy, stirring up clouds of debris.
Then one of them – I swear this happened – shot up to the surface like it was launched from a catapult, grabbed what looked like air, and zoomed back down to rejoin the group. I freaked out. Called the fish store thinking my water was bad, my filter was broken, something was seriously wrong. The guy laughed at me. Apparently corydoras just… do that. They breathe air sometimes. It’s totally normal and I’m an idiot for not knowing.
So obviously I went down a research rabbit hole that lasted until like 2 AM.
Turns out there are over 170 different species of corydoras and the pet trade just calls them all “cory cats” like they’re interchangeable. They’re absolutely not. I learned this the expensive way when I decided my bronze cories needed friends and added some peppered cories without checking anything. Bronze cories like it warm – around 76-78°F. Peppered cories prefer it cooler, like 70-72°F. For months I basically had one group of sluggish cold fish and one group of uncomfortably warm fish. Neither group was happy until I set up a second tank with proper temperatures for each species.
The substrate thing is where most people screw up, including me initially. Everyone says “no sharp gravel” which, okay, true. But I was using regular smooth aquarium gravel thinking that was fine. My poor cories were trying to exhibit their natural foraging behavior but couldn’t properly sift through the chunky gravel. Their barbels started looking worn down from constantly rubbing against the coarse substrate.
Switching to sand changed everything. Pool filter sand from Home Depot – $6 for a 50-pound bag versus like $20 for five pounds of “aquarium sand” that’s literally the same thing. Suddenly my cories were diving face-first into the substrate, filtering food particles through their gills, doing all this amazing natural behavior I’d never seen before. They looked like tiny underwater pigs rooting for truffles.
Feeding them properly took me way too long to figure out. I kept waiting for them to eat the leftover flakes from my tetras, thinking they were scavengers. They’re not scavengers – they’re active hunters that need their own food delivered directly to them. High-protein sinking pellets, frozen bloodworms, stuff like that. These are carnivorous fish despite looking like gentle garden gnomes.
The social aspect is probably the most important thing that gets ignored. Pet stores will sell you three cories like that’s adequate. It’s not. Six is bare minimum, but honestly eight to twelve is so much better. I’ve kept both group sizes and the difference is dramatic. Small groups act nervous and hide constantly. Larger groups are confident, active, constantly exploring and interacting. It’s like the difference between three awkward people at a party versus a whole friend group having fun.
My current group of ten bronze cories has distinct personalities that I can actually recognize. There’s one I call Scout who always leads the exploration parties into new areas of the tank. Another one – Fat Tony, obviously – camps out near the feeding spot and somehow always gets there first when food hits the bottom. One neurotic individual who spends half his time wedged behind the heater for no apparent reason I can determine.
When they sleep, they do this thing where they pile up in the weirdest configurations. I’ll find three of them stacked vertically against the glass like a fish pyramid, or five of them crammed under a piece of driftwood that barely fits two. Sometimes one will just… balance on top of the group. It’s ridiculous and adorable.
During cooler weather they sometimes spawn randomly. I’ve found clusters of eggs stuck to plant leaves or the glass, though they don’t protect them at all. The eggs usually get eaten by other fish before hatching, which is probably for the best because cory fry are incredibly tiny and would need specialized food I don’t have.
Water quality matters but they’re pretty forgiving compared to some fish I’ve kept. I do 25% water changes weekly, keep ammonia and nitrites at zero, nitrates under 30 ppm. Nothing crazy. The important thing is consistency – they hate sudden parameter swings more than gradually shifting conditions.
Tank size is bigger than you’d think for fish that spend most of their time on the bottom. A 20-gallon long is minimum for six cories, but they really shine in larger tanks with more floor space to explore. My 40-gallon breeder with the ten bronze cories is basically constant entertainment. There’s always some little drama happening – territorial disputes over the best feeding spots, group expeditions to investigate new decorations, random bursts of activity where they all start swimming laps around the tank together.
If you’re thinking about getting cories, start with bronze or peppered varieties. They’re hardy, cheap, readily available, and display all the typical cory behaviors without being finicky about water parameters. Once you understand what they need and how they act, you can branch out to fancier species like pandas or sterbai cories that are prettier but more demanding.
The biggest thing I learned is that these aren’t maintenance fish – they’re legitimate pets with complex behaviors and social needs. Watching my group forage and interact is honestly more entertaining than most of the flashy centerpiece fish I used to focus on. Sometimes the best fish are the ones you almost walk past because they look boring at first glance.
Trust me on this one. Those dumpy little catfish are way cooler than they appear.
Priya proves aquascaping doesn’t need deep pockets or big spaces. From her San Jose apartment, she experiments with thrifted tanks, easy plants, and clever hacks that keep the hobby affordable. Expect honest lessons, DIY tips, and a lot of shrimp in tiny jars.
