Persian loach

Where they come from

Persian loaches (Oxynoemacheilus persa) come from fast, clear streams in Iran. Think cool water, lots of oxygen, rocky bottoms, and current you can actually feel with your hand. If you set them up like a generic community tank, they usually look fine for a while... then they slowly fade, get skinny, or start hiding all the time.

Setting up their tank

Give them floor space and current. I would not keep them in anything smaller than a 20 long, and bigger is easier because the water stays steadier and you can build a real flow pattern. They spend most of their time on the bottom, wedged between stones, cruising edges, and darting into the current for food.

Substrate is a big deal with these. They like to nose around, and they can scrape themselves up on sharp gravel. Sand or very smooth fine gravel works. Then add rounded river stones, a few larger rocks, and some wood or roots to break lines of sight.

• Tank size: 20 long minimum, 30-40+ gallons is more forgiving
• Substrate: sand or smooth fine gravel (skip sharp stuff)
• Hardscape: rounded stones and rock piles with stable gaps (no wobbly stacks)
• Plants: optional, but choose tough ones (Anubias, Java fern) and wedge them into rock/wood
• Flow: aim for a steady current across the bottom, not just surface ripples

For filtration, I like an over-filtered setup: a canister or strong HOB plus a big sponge or powerhead. You want high turnover and lots of gas exchange. Point flow along the length of the tank so you get a "river" lane, then quieter pockets behind rocks where they can rest.

Water parameters: neutral-ish is fine for most captive fish as long as its stable and clean. They do not tolerate dirty bottoms. I vacuum around rocks regularly because mulm builds up in exactly the places they like to sit.

• Keep nitrate low with steady water changes
• Add extra aeration if your room runs warm
• Cover the tank well - stream loaches can jump when spooked
• Give them multiple hides so one fish cannot claim the whole bottom

What to feed them

They are bottom pickers and micro-predators. In my tanks they ignore most flake once it hits the surface chaos, but they light up for anything that tumbles in the flow and lands between the stones. If you only feed one sinking pellet a day, the boldest fish eats and the shy ones slowly starve.

• Staples: quality sinking pellets and small wafers (not just algae wafers)
• Frozen: bloodworms, brine shrimp, daphnia, chopped mysis
• Live (if you can): blackworms, grindal worms, mosquito larvae (where safe/legal)
• Occasional: Repashy-style gel foods pressed into rock crevices

I like small amounts twice a day rather than one big dump. Drop food into the current so it scatters and sinks into different spots. You will actually see them "hunt" along the substrate, and they keep weight on better.

How they behave and who they get along with

Persian loaches are busy, alert, and a little spicy with each other. You will see short chases and posturing, especially if you only keep one or two or if the tank is too bare. In a group with enough cover, the drama stays pretty harmless and you get more natural behavior.

• Keep them in a small group if your tank size allows (3-6 is a good starting point)
• Expect pecking-order stuff around favorite caves and feeding spots
• They are not a "hide all day" loach if the tank has flow and rockwork

Tankmates: think other fish that like cooler, oxygen-rich water and will not bully the bottom. Peaceful danios and smaller barbs can work, along with some other stream loaches if the footprint is big enough. Avoid slow, long-finned fish that get stressed by current.

Breeding tips

Breeding these in home tanks is possible in theory, but it is not common, and most people never see it. In the wild they are seasonal spawners tied to temperature shifts and changing flow. If you do want to try, you are basically playing "spring flood" with your aquarium.

• Condition adults with heavy feeding of frozen/live foods for a few weeks
• Do a cool-water period, then gradually warm a bit while increasing flow and water changes
• Add lots of small rock gaps or a coarse spawning mop-like area where eggs can fall out of reach
• If you see chasing and belly-heavy females, feed lightly but keep water changes frequent

Common problems to watch for

Most issues with this species trace back to warm, stale water and not enough food reaching the bottom. They can look "fine" right up until they suddenly are not. Get in the habit of watching their bellies and their breathing. Those two tell you a lot.

• Fast breathing or hanging in high-flow only: low oxygen, high temp, or dirty water
• Sunken belly: not enough sinking food, too much competition, or internal parasites
• Clamped fins and hiding nonstop: stress from tankmates, lack of cover, or unstable water
• Scrapes on the belly/sides: sharp substrate or rough rocks
• White spots after a temperature swing: ich (they are not immune just because they are loaches)

One more practical thing: they are escape artists. If you have gaps around hoses or a loose lid, they will find it eventually, usually at 2 a.m. I block openings with sponge or mesh and keep the waterline a little lower.