Rock catfish

Where they come from

Rock catfish (Rhamdia laticauda) come from Central America, where they hang around rocky streams and river edges. Think shaded water, lots of structure, and a mix of calmer pockets and faster flow nearby. They are built for wedging into cover and coming out on their schedule - usually after the lights go down.

Setting up their tank

If you set these up like a typical "community catfish," you will be frustrated. They are strong, secretive, and messy in the way most bigger predatory cats are. Give them space and give them hiding spots they can actually fit into.

• Tank size: I would not keep one long-term in less than a 55 gallon, and bigger is better. If you want tankmates, aim for 75+.
• Substrate: sand or smooth gravel. They spend a lot of time on the bottom and sharp stuff will rough up their barbels.
• Cover: real caves (rock piles that cannot shift, PVC sections, big driftwood hollows). Make multiple hides so they do not claim the only good spot.
• Filtration: overfilter. They eat heavy and poop heavy. A canister or big HOB plus a sponge prefilter is a nice combo.
• Flow and oxygen: moderate flow and good surface agitation. They handle warm water fine, but they do not love stale, low-oxygen setups.
• Lighting: they do better with subdued light and shaded areas. Floating plants or wood cover helps.

For parameters, shoot for "normal" tropical freshwater and keep it steady: mid 70s to low 80s F, neutral-ish pH, and low nitrate. The numbers matter less than clean water and consistency. Weekly water changes are not optional with this species if you feed them like you should.

What to feed them

They are opportunistic predators and scavengers. In my tanks they quickly learned the feeding routine and would cruise the bottom like a little submarine once food hit the water. They are not algae eaters, and they will not stay healthy on leftover flakes.

• Staples: sinking carnivore pellets, quality catfish sticks, shrimp pellets
• Frozen: krill, shrimp, mussel, bloodworms (for smaller fish), chopped prawn
• Fresh: earthworms are gold (rinse them well). Occasional pieces of fish or clam work too.
• Avoid as a main diet: feeder fish (parasites, thiaminase issues, and bad habit-forming)

Portion control matters. They will keep eating if you keep offering. I do smaller meals 3-5 times a week for adults, and I watch the belly line. Slightly rounded is fine. Stuffed like a sausage is asking for trouble.

How they behave and who they get along with

Expect a mostly nocturnal fish that becomes bolder once it feels secure. They are not "mean" in the cichlid sense, but they are absolutely a predator with a big mouth and a strong body. Anything that fits will eventually be tested.

• Good tankmates: sturdy mid-to-large fish that will not be swallowed (bigger tetras, larger barbs, robust livebearers in hard water setups, medium cichlids with compatible temps and temperament)
• Questionable: other bottom dwellers (they compete for caves and food), slow fancy fish, long-finned fish
• Avoid: small tetras, guppies, small catfish, shrimp - basically snack-sized animals

With multiple rock catfish, space and hides decide whether it works. A larger tank with several caves can work, but in tighter quarters you can get one dominant fish that hogs the best shelter and keeps the others stressed and pinched out at feeding time.

Breeding tips

Breeding Rhamdia in home aquariums is not common. They can spawn in captivity, but most hobbyists never see it because you need mature fish, lots of space, and the right seasonal cues. In the wild, rising water and big water changes tied to rain cycles are a trigger for a lot of river catfish.

• If you want to try: start with a group of juveniles and grow them out (sexing is not straightforward)
• Provide cave choices: deep, dark tubes and rock caves are the usual spawning sites for cave-spawning cats
• Simulate rainy season: cooler water changes, then gradually warmer and heavier feeding
• Be ready to separate: adults may guard, or they may eat eggs/fry depending on the individual and tank setup

Common problems to watch for

Most issues with these guys come down to three things: dirty water, injuries from rough decor, and overeating.

• Barbel erosion: usually from sharp gravel, dirty substrate, or chronic high nitrate. Switch to sand, vacuum the bottom, and increase water changes.
• Hiding nonstop and not eating: often too bright, too exposed, or being bullied at night by other bottom fish. Add cover and feed after dark.
• Scrapes and split fins: they wedge into tight rocks and can come out with abrasions. Smooth your hardscape and avoid sharp slate edges.
• Bloat/constipation: too much rich food too often. Back off feeding, offer a fasting day, and use higher-fiber items like earthworms occasionally.
• Ich and other parasites: they are not magically immune. Quarantine new fish and do not rely on "clean" feeder fish.

If you keep up with water changes, give them real caves, and feed like you mean it (but not like you are fattening a pig), they are tough fish. The "advanced" part is mostly that they get big, eat big, and will absolutely take advantage of sloppy stocking choices.