Which nano do you have ??? Is it one of the basic all in ones ???
I had a Tunze 9002 on my BC29, and it is REALLY sensitive to water level changes, which happened fairly quick in my tank. It would be skimming great when I left for work, but when I got home 12 hours later the water would have dropped some and it wouldnt be skimming. I went with a sapphire after that and had decent results but I do believe theyre out of business....
That being said, I had my BEST success with water parameters simply by doing 5 gallon water changes every week, or every 2 weeks at the most. I dont think its necessary to have a skimmer on most of the nanos when you can just do small water changes more often, but thats just me.....
You could always look at a HOB type if you have room behind the nano.