Just done a quick google search for the Berlin 90 and seems a reasonable price. Worth trying it out, better than not using one at all.
I'm kinda in the same boat as you. I havent actually got a skimmer on my 180L marine tank and my nitrates are at a reasonable 5.0 due to weekly 10% water changes. Tank has been running since November. You might be interested in 2 products by Seachem: