Stream catfish

Where they come from

Stream catfish (Pseudobagarius macronemus) come out of fast, rocky rivers in South and Southeast Asia. Think clear water, lots of oxygen, strong current, and endless cracks between stones. If you set the tank up like a lazy pond, they just never look "right" - they sulk, breathe fast, and act stressed.

Setting up their tank

This is one of those fish where the tank setup matters more than fancy food. You are basically building a slice of river: flow, oxygen, and rockwork first. Everything else is secondary.

• Tank size: I would not keep one long-term in less than a 4 ft tank. Bigger footprint beats height every time.
• Flow and oxygen: strong circulation plus airstone or venturi. If you can see the surface really moving, you are getting close.
• Filtration: over-filter. They like clean water and they eat meaty foods, which means waste.
• Hardscape: smooth river stones, rounded cobble, and lots of tight caves. I stack rocks so there are several "personal" crevices.
• Substrate: sand or fine gravel. Skip sharp stuff - they wedge themselves into gaps.
• Lighting: keep it on the dim side or use floating plants. They are much bolder with shaded areas.
• Temperature: mid-70s F works well (around 24-26 C). Stability matters more than chasing a number.

I also like to arrange the rocks so I can still get a siphon in there. They are messy eaters, and little pockets behind stones can turn into a crud trap if you cannot reach them.

What to feed them

They are carnivores and they eat like a predator that is used to food washing past in current. If you only toss in a couple pellets and walk away, the faster fish will steal everything and the catfish will slowly get skinny.

• Staples: sinking carnivore pellets, good quality wafers with a high protein base
• Frozen foods: bloodworms, blackworms, mysis, krill, chopped prawn/shrimp, chopped mussel
• Occasional: earthworms (rinsed), small pieces of fish flesh (not oily, and not often)

Go easy on very rich foods at first. In a warm tank with heavy feeding and big flow, things can still go south fast if leftover meaty bits get trapped in the rocks.

How they behave and who they get along with

They are a mix of shy and bold: shy in a bare tank, bold in a tank that has current and lots of cover. Mine spent the day wedged under rocks with just the head sticking out, then turned into little ambush hunters once the room lights went down.

They can be territorial, especially with their own kind or other bottom fish that want the same cave. You will see posturing and shoving over prime crevices.

• Good tankmates: fast-water barbs and danios, hillstream loaches that have their own niches, larger rasboras, other midwater fish that do not poke into caves
• Use caution: other bagrid catfish, botia loaches, any cave-hogging species
• Avoid: tiny fish that can fit in their mouth, slow fancy fish, long-finned fish that get nipped, anything that needs calm water

Breeding tips

Breeding them in a home aquarium is not common. Most of what shows up in the hobby is wild-caught, and these fish tend to want seasonal cues and very specific spawning sites (deep crevices, heavy flow, and cooler-water changes).

If you want to take a swing at it, your best bet is to run them like a river biotope and mimic a rainy season: heavy feeding for a few weeks, then a series of cooler water changes with stronger flow. Provide narrow rock cracks and pipe caves where a pair could tuck in and defend a clutch.

Common problems to watch for

Most issues I have seen with this species trace back to three things: not enough oxygen/flow, a tank that is too "new," or injuries from squeezing into the wrong rocks.

• Fast breathing or hanging in high-flow areas: usually oxygen is low or the water is dirty
• Not eating and hiding nonstop: too bright, not enough cover, or being outcompeted at feeding time
• Scrapes on head/barbels: sharp decor, rough rock edges, or getting pinned in tight gaps
• Bloat/constipation: too much rich food, not enough variety, or a fish that is eating big chunks too often
• Ich/velvet after purchase: common on wild fish stressed by shipping and warm, low-oxygen holding tanks

Quarantine helps a lot with wild-caught specimens. I keep the QT tank dim, add extra aeration, and offer small meals until they settle. Once they are eating confidently and not breathing hard, they are usually much tougher than people give them credit for.