Fluval tubing argh what a pain !!!!!!

Hi I've got a Fluval 204 canister filter and I want to add a UV steralizer to the output however I really hate the ribbed hose that comes with the filter and ideally I'd like to get some proper rubber tubing. Has anyone done this before ?. What diameter is the tubing and what size rubber tubing do I need to replace it.

Also I've never had a UV sterilizer before and I'm interested in hearing peoples opinions on them. I've heard stories they effectivly lower fish immune systems cos they're not been subjected to bacteria etc anymore, does anyone have any proactical experience of this or is it just hear say ????.

Well I've recently added some more fish, 8 black molies and 8 platies and for the last 2 weeks I've lost 5 of my platies, each one seemed to die without any obvious symptoms, then today I noticed my 3 clown loalches hlad white spot, so I'm now treating with white spot control treatment, I realise you can't use UV at the same time as treating a tank with chemicals but my theory is if I had UV then there would be less chances of out breaks of ICH and fungus etc.

Basically my tanks contains mainly livebearers, I like moliwes and swordtails and I've got about 25 fish altogether in a 50 gallon tank, most of the time there all happy but every now and again I lose a fish, I know my ammonia and nitrates and fine cos I test for that about once a month and my last test came back okey but I just wonder whats killing the fish every now and again. As i say though the loss of 5 platies all in the space of 2 week had me really concerned and to find whitespot today has caused me to think that perhaps UV us the way forward ???