Myxazin would be OK as a just in case as it will deal with fungus / bacteria. Start with half the recommended dose and monitor the effect on the clown, then if the clown seems OK give the second half of the dose 12 hours later and monitor the loach again.
It is hard to offer a really sound treatment without seeing the fish, I still think this fish is depressed/lonely and therefore stressed.
If you are near the Wirral there is a chap who has many smaller ones at the moment but he won't post you will need to collect.
There is also a company advertising clown Loaches on E-Bay who will post.
ok thanks
i hve bought some catfish sinking pelets for him to eat as i was feeding him flake food and was told that it wasnt the right food to feed him
hw does not seem to be eating
how can i get him to eat something
You may find he likes blood worm, snails and cucumber, I have a group and they hide until the bloodworm come out then its a frenzy, they darken up after the bloodworm and get paler a day or so after eating it (I give it to them every 3 days) they also come out at night and clear up all the baby MTsnails that appear but all of them turn their noses up at pellets and flakes.
Clowns have a habit of lying in positions that for any normal fish would look like they were on the way out upside down, sideways squished in holes you name it. If he looks proportionally skinny try feeding him up with a meaty food and see if that helps, but definitely lots of hidey holes, some bubbles and some friends see here Trimar theres good reviews about this guy and they have loaches for uk delivery. Careful not to medicate in panic until you know its definitely not just malnutrition which has made him weak and susceptible. Purely based on experiencing my loaches behaviour no medical opinion offered (although if you've had him eating for 3 years only for him to stop now it may be bacterial or parasitic...)