need advice

I have the coralife 125. It does take a bit of a learning curve to get the thing running nicely, but it can be done. First thing is to ensure that the venturi piece and the pump are tightly pushed together - any leaks will diminish bubble production. Set the skimmer so you see it slowly pushing a layer of "dirty" bubbles to the top of the cup (this layer will probably go up and down a number of times before it overflows into the cup). Check it about half an hour later to make sure this setting has held (occasionally pressure can build in the outlet hose, which leads to an overflow of the cup - so it's important to check that your setting has held).

After a day or two of skimming, sludge will probably build on outlet tube into the cub, so VERY, VERY slightly raise the bubble level of the skimmer. Leave it for 10 minutes, if you don't see bubbles coming out the top, try raising it just a little bit more.

All in all, it does a decent skimming job - it's just very fussy.
 
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