The fission nano skimmer is the biggest waste of $30 bucks I've ever made. Unfortunately for me, I read the hundreds of negative reviews AFTER I bought the P.O.S.
What are the problems? Jeez... where do I start...
Firstly, the cylindrical foam intended to filter the microbubbles does a horrendous job. This nano skimmer was popular with the nano-cube owners because of how nicely it fit into the back of the JBJ 24 I believe.... there's a MOD.... a FRIGGIN MOD just so you can eliminate the microbubbles. Else, you'll be stuck with those microbubbles...
Secondly, once it clogs, (and yes, it WILL clog sooner or later), you'll find it nicely overflowing right through the top of the skimmer.
Now.... all this wouldn't really be a problem... IF it did it's job (pulling tea-colored/brown skimmate out of the tank). But it doesn't.... surprise surprise. The best you're going to get is a very very very light tea colored skimmate, but I wouldn't be surprised if you get nothing but white froth. .... which is my third point.... It doesn't do it's job.
But there's a plus side!.... The little pump it comes with sure packs a punch for its size. Other than that, don't ever buy that skimmer....
It isn't even worth 30 bucks... I don't care how nicely compact it is... it's just a pump blowing microbubbles into your tank.
Also... I forgot to mention... The water level at which this skimmer sits in, is EXTREMELY important for correct function.... a few centimeters off you are from the intended level, and you might as well remove the skimmer.
If you have a 12 gallon nano.... don't bother skimming at all.... There's just too many BEAUTIFUL skimmerless nano-reefs to prove this.