QUOTE(advocado @ Apr 9 2012, 09:12 PM)
Just checking, is it normal for the water to turn abit milky green when you squeeze them hard in a cup of water once a week?
Yupe, pretty normal, marimo do have metabolism as well 
Regarding fake Marimos, other than normal moss in a pingpong ball, styrofoam, I found out Japan are selling artificial marimo's that looks like real ones, difference is it's made of wheat & ceramic, so just wondering how exactly can we tell the real thing from fake?
Will fake marimo bubble after you clean them up?
This question too subjective as conditions vary according to the "type of the fake marimo"Will real marimo continue to bubble in water or just for a while?
Not really, it is heavily rely on your tank setup, lightning condition, PH level and also freshness of your waterWill they turn brownish or loose color?
If you are referring to the real marimo, YES if owner neglect them, especially exposed to direct sunlightWill they stink slightly after 1 week of not squeezing & smells like plant after cleaning?
Depends on your water condition but the smell part is pretty normal for marimo, you will smell the smell like vege algae, something like that haha Will they float after squeezing/cleaning and sink after half a day or so?
as answered above regarding water conditioningWill real one feel bouncy when you squeeze them or will they split apart?
Yupe, bouncy feeling like hard spongeI got curious so i used a satay to poke tru the middle to check one of the not so healthy ones and even though it's bouncy when you squeeze it the inside core seems to be fluffy, but takes abit of strength to poke tru the whole body.
Pity Satay Marimo 
Also i notice some of the forumer's marimo tend to have rather long "furs".
Long or short furs doesn't mean anything, you cant judge the genuineness of the marimo via its length of furs as claimed by some unscrupulous sellers, the most important thing is the growth rate
. Btw, with proper trimming/maintaining on its body, you will obtain similar effects On top of all answers above, I as a marimo seller for many years, there is a member pop me a question today, how to differentiate grade A or grade B on your marimo, I felt this is pretty funny as some sellers attempt to create their own
Grading System to grade their marimos, these grading are created by their own as gimmick to attract buyers and at the same time low down others reputations. IMHO, there is no such Grade A B C D etc bla bla bla, if Crystal Shrimp then got Grade CRS etc la, a big nono to marimo, no such grading system unless named by ownself