when i first started there weren't the test kits around as much
and my dad had kept fish as well
i find your fish can tell you what is going on in the tank
fish at the surface can mean not enough surface agitation, and polluted water
sitting on the bottom, can mean their cold
clamped fins water parameters out of whack\
there are other things that can cause these symptoms as well
generally speaking if there is a problem i do a water change first