Tunze 9004 DC not breaking in


New member
Hi, I just got this skimmer and been running it on my old tank to break it in before I set up my new Fijicube 32g AIO. It's been 4 days and it's still not producing any skimmate. I have the airline almost fully open (see 2nd pic), and the skimmer is at the correct height with a little less than 1/4 of the grill submerged (see first pic). I've played around with both the height and the air intake but no luck. The bubbles are going about halfway up the tube. I've checked all the equipment and it's all setup correctly. Any ideas?


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Well-known member
Several ideas- I am seeing skimmate (the second picture shows some good "dirty" bubbling), and with this style of skimmer, there are times when that is actually a median production level. Also- it can take a good long time for a skimmer to acclimate and really get going even exceeding a number of days. As well, your tank conditions may not be ideal for heavy skimmate; for example, the water might actually be very clean. It may even be the specific gravity- a slightly larger sg reading can sometimes help as the water is so to speak more "dense."


New member
I have the Tunze 9012 DC and it took at least 3-4 weeks to be okay. I see skimmate on your picture so just let it be and empty it when needed, even if 2-3 times a day. It needs to break in and there has to be a film build-up inside of it before it starts doing a good job. These are good skimmers, you will like it. Just be patient.


New member
Thank you guys! Finally started getting some real foam yesterday. it's inconsistent but i'll be patient. Part of the issue is I'm switching tanks so the water has some sediment.