changing coolant

so im trying to understand here

i saw mentioned that some peeps change out their coolant 2 and 3 times per year ... hell i dont even change the coolant in my vehicle but once every 3years and im pretty sure that goes thru ALOT more abuse than my comp

so assuming everything is optimal ... comp and wc is setup and stabile ... not constantly retweeking etc ... keeping fluid levels up regularly ....

how often should one really change the coolant

Can't really answer your question but I would like to point out that computers do not get as hot as cars. The extreme heat in an automobile will kill any algae.
I had my pump fail a couple of weeks ago. When I drained the system and blew out the hoses, there was some stuff in the coolant which I never noticed before. It is a sealed system but I was using silicone tubing at the time so I was always adding distilled water to the system every 3 weeks or so.
I can only guess that the "stuff" in the old coolant was the beginnings of algae. I had the system in service for about 8 months before the pump failed. So.. I am going to service my loop every 6 months or so.

Everytime I work on my system, I change out the water. That turns out to be about 3-4 times a year

depends on what coolant combo you are using. If you are using distilled, you should already have some anitfreeze and some iodine in it, so i wouldnt really worry about growth.

as for other coolants, i am not sure. if there is nothing growing or the water isnt discolored, than i woudlnt about it.

If your coolant gets dirty it can really kill performance too.. especially with thin pin style design blocks or jet impingment style blocks (just about all blocks basically..) at little bit of crap built up can really go a long way...

Some people change like once a year, and some change fluids every few months. I think that if you are using something like iodine to kill growth, twice a year is reasonable. I prefer to flush and fill avery 3-4 months or so just to be cautious.

I read somewhere that some use alcohol for algea control. I have a mix of UV additive, distilled water and a bit of alcohol. Anything wrong with using alcohol?

No but be careful if you have acrylic because alcohol can crack it.