I'm far from an expert on clown loaches. I can tell you that they'll outgrow your 55. You'll need at least another 20 gallons to keep them happy. Sounds like you're doing great with them so far, though.
Many fish make noises. It's nothing to worry about. My synodontis isn't called a "squeaker" for no reason.
75: blood parrots, featherfin cat, emperor tetras, turquoise rainbowfish, BN plecos, japanese trapdoor; 46: WCMM, gold inca snails, ghost, bamboo & amano shrimp, kuhli loaches, rummynose & ember tetras, endlers, platies, flame gourami, guppies; 16: pygmy, peppered, loxozonus corys, otos, assassins, RCS ... ~ Research PRIOR to purchase.... ~