So my computer is fully watercooled and a couple of days ago I noticed mold in my res. Someone mentioned using white vinegar to clean out all the blocks res and rads.
Have any of you used this method before? Or do you have any tips?

Vinegar is best.  Put a silver coil in the reservoir, that will kill the mold and bacteria when you refill the loop.  Very simple way to keep the loop clean and running well.  Might also clean it a bit more often, like once a quarter or twice a year.  Not sure when the last time it was that you had cleaned things out but a regular cleaning can do goods things.  It's like not changing the oil in your car on a regular basis.  You would never do that.

the weird thing is, is that I have a coil in it. it hasnt even been a year since I've cleaned it last as well.
 
And Thank you very much everyone! <3

tet5uo
I have had the same coolant for 2.5 years. Just topping it up every few months. There is enough chemical in there to not have anything growing. 
 
Just make sure you use some coolant with additives , that silver-coil isn't  enough to kill everything, they're kinda BS. You don't want cooties growing in your loop.

What specific additives are you referring to?  I'm due to flush my system now.

tet5uo
I have had the same coolant for 2.5 years. Just topping it up every few months. There is enough chemical in there to not have anything growing. 
 
Just make sure you use some coolant with additives , that silver-coil isn't  enough to kill everything, they're kinda BS. You don't want cooties growing in your loop.

I use a silver coil with distilled water and have never had any build up or mold growth.  I flush the system about once a year.  I think a good cleaning before assembly, final rinsing everything with distilled water, is enough to prevent build up whether you use silver + distilled or coolant with additives.

In my experience I have found that putting the silver coil in the return line to the reservoir forces most of the water to pass over the silver coil. Doing this along with distilled water I have had absolutely zero issues and I clean everything every two years.

In general Distilled water and a Silver coil is enough, however with a large loop that has substantially more water in it,  it may not be enough.  ***ALSO*** if the comp is on a desk near a window, I have had this happen personally, I had a curtains partially open for some natural light, and had sunlight hit the side of the case, and in a few months, I had small amounts of algae growing on the tube sections that had direct sunlight, so there are some variables there.  Once it happened it was really a "well, DUH!" moment for me, but I never thought about it.  Since then, I moved the case over a little so there is no direct sunlight on it.
So there can be things that actively work against a clean system.
 
Distilled and a Silver coil is all that is needed most of the time, you can use a premix, but most I have used, if I don't dilute them tend to clog up blocks after a while.  If you want a silver coil and a separate additive, I recommend using this this and this specific type as it is not Copper Sulfate, which when mixed with silver can have issues with copper and/or Nickel, not always but it can, but this variant of PT Nuke has Benzalkonium chloride.  You can add in a few ounces of packaged coolant, this will also help with corrosion on top of the protection of various types of growth.  I currently use Distilled water, a silver coil, PT Nuke with Benzalkonium chloride (only a couple drops), and a couple ounces of Feser One per quart/Liter of water and have had ZERO algae/mold since, maintain GREAT temps and have not had any clogged blocks. 
 
At some level, your mileage may vary, but this is the combo I have had a lot of success with.

I use distilled and PHP nuke. Also if vinegar is left in your loop for extended period of time it will reacte with the solder and copper and start eating it away. What i recommend is replacing the tubing with new stuff,clean all the blocks with a toothbruch and some lemon juice then rinse everything out with some distilled water (u can boil some and use it to flush out the rads helps get rid of gunk).If u have already used vinegar make sure u rinse everything really good. Good luck

I have mostly Swiftech parts and use their HydrX additive. I only change out my system when a new part is needed, so it can be well over a year between flushes. Every now and again it needs a top off. I use two of the HydrX bottles, my systems uses about 1/2 gallon of distilled water. Never had mold or anything else in it over about 8+ years of watercooling.