Last Friday I picked up a small, single head duncan to add to my nano. It is getting gentle flow below the outflow of my filter. However, it is only extending tentacles on one side of it's oral disc. Is this a sign of too much flow on one side, or a different issue? Sorry I can't take a better photo, my lights are mostly blue and I have no orange filter.
if you really are keeping up with water changes at that level and your not having algae problems, feeding stupid heavy, your parameters are probably fine. Test kit would be nice to have, but that line, what are you parameters, makes me think of the seals squeaking in finding Nemo lol....I imagine its a nano if your changing 40% water a week, insure your salinity is ok, and not a bad hydrometer or a out of calibration refractometer.
My question would be how long have you had it, and is it a flow issue, feeding will strengthen them up too and make them deal better with flow, if its new from a shop and hasnt eaten in a while