others may feel differently than i do, but here's my opinion, for what it's worth.
i would never randomly try a medication without first establishing to the best of my ability what exactly the problem is. even once i had it narrowed down, i would first opt for any non-medicated forms of treatment if at all recommended (for example, with
ICH, i'd raise the temp and do more water changes, rather than medicate). when medication is called for, i'd consider all the tank occupants (i have no hospital tank) to see how they could tolerate it before actually dosing them (so as not to kill any 'scaleless' fish, etc).
anyway, my questions for you would be... what are the symptoms? what fish are affected? how long has it been going on? how often are you doing water changes? your nitrites and nitrates might be a little high for discus, but i'm not an expert on their care, so perhaps someone else can help with that. the loaches are likely particularly sensitive to medication, so use caution with what you select.
anyway, with more information maybe someone here can be of more help. without it, i couldn't recommend for or against any particular medication.
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I'm glad to hear that things are looking better in the tank. 
