Yellow Water

[waterbear]

When metal ions in the water are oxidized (by shocking) they will form colored compounds in the water. This is what colors the water. When they precipitatate out of the water they form stains. Pools that are stained often don't test positive for metals since the metals are no longer in the water.
A full set of tests results, including metals, will let us know what is happening in your pool, including the possiblity of staining if metals are present.
Green water ususally indicates copper
Yellow to brown water ususally indicates iron
Purple water usually indicates manganese.

[mbar]

I am thinking that something you used may have had some chlorine in it, and gave you a little of the lime-ade coloring you get when you put chlorine in a baquacil or non chlorine pool. As the chlorine goes away, the color probably will too. Just a thought.

[waterbear]

It was my understanding that E-Z Pool/Chlor-Free is not biguinide but some sort of propiretary mixture (I would guess sodium percarbonate as the main ingredient since it's level can be tested with DPD) that is supposed to eliminate the need for chorine. I don;'t believe it is EPA approved.
http://www.americasbestpoolsupply.co...1/PageNumber/1
http://www.ordinis.com/chemistry/e-z_pool.htm
http://www.rogerspools.com/chemical.htm
There is also an ionizer called Chlor-free.
http://www.chlorfreeglobal.com/how_works.php
http://www.chlorfreeglobal.com/product.php
In either case I would have the water tested for metals. I would also recommend switching to chlorine.

[mbar]

Wow, I didn't know what it was! Sounds like it is a mineral based product - which could lead to stains. Thanks waterbear!