Bubbleponics: How often do I change the water

I've heard two weeks is good, but doesn't the plant go into shock if i keep taken the roots n and out of water every two weeks?!?...only for like 4 seconds or so out of water

An air bath is good. Most change the res weekly although some go longer at times.

is two weeks good?

Ive been a month without changing with zero % algae in my resevoir....I try and do it every week to two weeks. Air baths is a important factor in seeing ur plant thrive. The root systems absolutely LOVE the huge amounts of oxygen they take in during these air baths. You will notice a huge difference if you give ur babies an Air bath.

if you are worried about emptying a res with out disturbing plants, submerge a small pump and get all but like 2cm of water, then fill with fresh nutes. My stuff is light tight so of coarse i haven't notice algae in a bit.

A full flush is a pain but I often do this: I have a drain valve on the res so drain it as much as possible (tilting it forward), then refill half way with plain water. Run the airstones awhile then drain again, refill and reset nutes. I do that at least every two weeks and anytime anything seems not quite right.

Another option...though one that is easier to do when first building your unit...is to put a drain spout/plug into the bottom of your unit. (Like the ones you see on those coolers you put Gatorade in to pour on unsuspecting coaches)

Then, just by keeping your unit elevated a tad bit (or tipping if you have to) you can easily drain from the bottom and not disturb the roots as much.

(Sadly...this is a lesson I learned the hard way when I built my first home bubbleponics unit and realized I was in the same situation you are in now)

what are signs on the plant that it's time to change the water and put in fresh nutes and ferts

rofl no hahahha

signs would be your water is getting low, your plant is having any sort of deficiency symptoms or looks weak, or if its been awhile you should change it, like if stuff is getting slimy or gross or whatnot... you'll figure it out.