ok, so this is a hard one to give a deep opinion… but, in short, if you are running one system id just pump the nutes through the chiller… the tube is stainless or titanium usually to make them suitable for salt water aquariums…
now where it gets hard is when you want to clean inside your chiller… there are several ways you can do this, bleach for example… peroxide… and if your using hydroguard and the chiller consistently you may only decide u need to clean inside it once-twice a year… less… where u need to clean it is if you want to stop using it for a while, you will need to clean it out, before u store it… then id say before you use it…
I now have 5-6 systems running off one chiller, I use the coils @Covertgrower they were not too expensive 4 delivered for $90 aud… I think… Alrighty.. One chiller, multiple hydroponic systems... how im doing it
and pumps and thermostats and controllers… but chillers are expensive. and I got the one for free… 
