The person who I bought my most recent clownie additions off claimed that a friend of theirs had a monster clown loach tank and some big (10") specimens in there. Evidently his cleaning fell by the wayside, so the bottom got very 'silty' but the one thing he kept up with was his filter maintenance, so there was a good flow in the tank and one day they looked in and saw a few tiny little baby clowns in there - deduced that they must have bred at some point! Which is very exciting if true!
From what I can gather, it's mostly about getting a good water current in the tank, and mimicking the river bed for the bottom of the tank. I've also read somewhere that feeding live food (guppies etc) can prepare the females for spawning.
I'm switching over to almost a clown loach only tank and have some nice big fish at around 7" so I'm just going to enjoy my tank, keep up the water flow, feed them all well and hope that one day they might just breed for me
We're lucky in that the females of every other species of loach we've had in our tank have become gravid very quickly after reaching sexual maturity so I don't know what we do (I should probably make note of the key factors though for future reference) but something about the conditions in our tank, or perhaps what we feed, makes female loaches fill with eggs so if clown loaches are anything similar to yoyo or zebra loaches in their requirements then we might stand some small chance!
I'm mostly about enjoying watching them though, so I'm not fussed either way. I love watching them swim up to the filter outlet to enjoy the current
It would be an absolutely amazing experience though - to breed clown loaches in the aquarium.
I believe they do have to be in reasonably large social groups to breed though, so a 'breeding pair' is not very true, in reality. I doubt you could sell a breeding pair of clown loaches and have them just get on with it in any old tank with other random fish.