nope, i never use the same equipement, each tank has their own equipement. I dont use water conditionner, i let my water age for a few days before and its been fine. the main tank has been running for about.....a decade, and the goldfish tank has been running for a year. the reason the goldfish were sick was because they were in a bag that would be too small for them (i think it was a large size bag with like 4 goldfish in there) and when i released them in the tank, i'd realize that they have ich! then i'd go through the battle of trying to save them. i think my goldfish are overly stressed but everything is now finally under control, thus, no more goldfish deaths. but i cant help my other aging fish...ugh, maybe ill just stick to something like arowanas or angels that should live for about a decade...well, i change the water quite frequently. once a week, lol, just when the water has aged well. actually, now that im thinking about it, i think its once every 2 weeks. 1 week for all my fish tanks, and 1 week for goldfish tank. i alternate, so it shouldnt be wrong cause ive been doing that for about a year and nothing has happened...
oh, another guppy died, lol, yes, she looked like she had fungus on her face, next day of the seperation she died, good thing my hospital tanks are just 1 gallon, not so much to wash!