I've owned clown loaches for a couple of years after my husband was excited about having them. We didn't know at the time that they could grow massive and that our current tank would be far too small for them.
We originally started with 4 and they were only about an inch long at that time. but then we saw less and less of them and became convinced that there was only 1 left alive. Our suspicion was confirmed during a house move last month with just the 1 clown loach hiding inside a large house decoration.
Later we learned more about them and how big they could grow, so we decided to pick some barbs with similar markings in a hopes he'd come out and socialise with them. We introduced them just a few days ago after waiting 2 weeks for the tank to settle. They make the tank so alive chasing each other around, swimming in groups, chasing after tiny slices of cucumber. The clown loach still prefers to hide in his new home a large castle hidden behind plants, but he comes out now and then and does his little dance by the water filter and then disappears back inside his private place. He doesn't seem too interested in the other fish yet, probably been too used to being on his own and being 3x their size, but he does seem to be popping out of his castle more often and lately his new display is swimming out one hole in the castle and back in another, then popping out of another hole and weaving back round to another hole at high speed like he's on a rollercoaster ride.
Some day we'll have to move him on to a new home if and when he gets bigger to a loving family with a larger aquarium and existing clown loaches to hopefully socialise with. I don't know any people where I live who keep them so that'll be something to look out for in the near future when he's getting noticeably larger and posing a threat to the smaller fish. It'll be sad to see him go when he has to but we simply cannot afford a larger tank and the only size of clown loach you see in pet shops are around 1 inch size with no warnings about how big they can get or what size of tank is recommended for them.