This is my first review so don't complain if there is insufficient info
I bought a Bubble Magus 3.5 needle wheel skimmer for my 18" x 17" x 16" nano tank. Total water capacity, inc. sump, is 90 litres or 24 gallons (roughly).
The skimmer works extremely well. It comes with inbuilt pump (of course, being a needle wheel) and overall is extremely quiet. It started producing skimmate on the second day and that was when I was only cycling the tank with live rock! No I have a fully stocked tank, the skimmer is doing an excellent job of producing skimmate. Sorry, I have not taken any pics of the skimmate - anyway, you all know what it looks like.
The skimmer operation / water level is extremely easy to adjust. However, you need to make sure that you fully the operating instructions and do not exceed the maximum height of the external water level otherwise you wont be able to back off the internal water level and your overflow cup will truly overflow.
Ignore the price in the following link, as that is not the Singapore price. I paid just over SGD$200 in Singapore. However, if you are going to HK, you can buy the same skimmer for almost half the price.
http://bubblemagusskimmers.com/catalog/bubble-magus-protein-skimmer-bmnac35-p-951.html?osCsid=6bd05e39f0a803c08579092ef7deb10a