Poorly Fish

hi, just recently 3 of my four platys are staying on the floor ,hiding etc...  there is no sign of white spot or worms,just they seem very distressed. one does have his fins down a fair bit of time but otherwise looks healthy..  any advice would be appreciated , thanks

hi, water quality is good, no nitrites ,ammonia etc ... as for feeding a bit hit and miss especially for one of them, he just seems listless.. i use nitro zorb in my filter and wondered if i could put some general tonic in with this or would i have to take it out ,

API's page on Nitra-zorb doesn't say anything about medication. But they do say it an ion exchange resin which is recharged by soaking in salt; nitrite and nitrate will be swapped with chloride (not chlorine) and ammonia with sodium. Depending what is in the tonic, most of it should be OK though salts would be affected by the ion exchange process.
Can I ask, where in the filter do you have the nitrazorb? Media like this should be placed last in the direction of water flow. Because it removes ammonia and nitrite (according to API) you don't want to starve the bacteria and placing it after the other media means there shouldn't be much left after the bacteria have had first go at it.

As for the platies, I'm not really much help. Try a tonic by all means but they don't usually do much. If there was some definite symptom to go by you could treat that, but it sounds as though there is nothing definite.

No the nitrazorb should be last. That way the bacteria get first dibs on the ammonia and nitrite and the nitrazorb only removes the amount that gets past them.