no reason to spend $25 on one when a bowel, empty salt bucket or what ever other container you have laying around along with the airline and valve as pictured above will do the same thing but for about a $1. plus in that pic of the system on amazon it looks like you need your water level to be very low in order to have the bag hang on the end. I don't know anyone that runs their tanks that low.
+1Dripping can be effective and not dangerous if done while keeping the NH4->NH3 conversion process in mind.
These threads make me feel so ghetto
I just use a binder clip I stole from work by clipping the black part to the tank rim and running some airline through the metal loops so one end is pushed under water, tie a knot in the airline and poke it through a hole in the lid of a styrofoam box. I start with a tight knot and loosen it gradually.
Be careful with temp if you use a bucket, it's nice how this product lets it stay at tank temp.
+1
Also, Prime is your friend.
For a lot of things dripping is more trouble than it's worth, like if you can just match a qt to your salinity and temp. But you can do it right if you pay attention to a few factors, and sometimes it is a good option to have.