kimi : i got same problem too. but as i think its normal becoz the water will dissipate after some time of use. its becoz the bubbles make splashes when it burst at the water surface inside the bubble counter. thus, the gas carries the evaporated water to the aquarium (not the co2 tank).
the trouble is that we need to refill the water once in a blue moon.
i kept mine going 24/7 on manual regulator, no on-off solenoid la...
*also, if ur tube is clear/transparent type, if there's water inside the tube from co2 tank to the bubble counter, then ur check valve got problem lo.... if there's water droplets after bubble counter but before the aquarium, i think its normal.
hope above helps. other sifus may chip in if i'm incorrect.

Added on August 3, 2012, 1:29 pmQUOTE(weijie @ Aug 2 2012, 04:08 PM)
jctasoga:
what is the ambient temperature? it is highly affect the performance of cooling fan.
yeps thats another alternative for auto-top. but for sure it wouldnt look nice if you have a coca-cola bottle on top of your nano tank.
i believe its 28c or 29c. as mentioned, there are 2 tank side by side. same setup. only 1 tank is with the cooling fan. so its a fair test. however, becoz its small tank, its easier to see the water temp swings. 1-2c on small tank should be faster to see the effect of temp swings.
This post has been edited by jctasoga: Aug 3 2012, 01:29 PM