They were fine with malawi water conditions (hardish water) , I didnt have to change anything, i had them for a couple of yrs in the malawi tank. although ideal water conditions for them are soft to medium it worked.
the only draw back i would say is that Clown loaches quite easily get white spot, so i would be careful if they dont like the conditions they will def come out with whitespot. I would keep an eye on them at first just to make sure. I never had this issue but have heard of this with CL's
the cichlids in the tank never touched them nor did the Clown loaches touch the cichlids, as they are more than able to look after themselves.
never tried with other loaches tho, and i would try to get some CL medium sized