Nitrates of 25 isn't life or death in a fish only tank, BUT it will become an issue with an anemone in the tank now. You have to get as close to 0 as you can to keep that thing happy. Not easy to keep, lol. I had one and returned it a few months later, just too much worry for me. hehe
But anyways, a skimmer can help some but it's not gonna get 25 nitrates down to 0. Thats gonna be water changes and feeding habits. I'm guessing with the fu man chu in there the bioload is bigger than what would be normal for a 30g tank, plus to be honest I don't know much about lionfish, I know that one is small, my friends happen to have one.
If you want to try a skimmer I would look at the reef octopus hang on ones or maybe a CPR back pak. You want to get one that is rated for 2x the size of your tank to be good, so you need a skimmer for 60-100g.
Here are some links
Hang On Back HOB Reef Octopus Protein Protein Skimmers - AquaCave.com
CPR Protein Skimmers - AquaCave.com
Eshopps In-Sump & Hang-On Protein Skimmers - AquaCave.com
These are all reputable and good quality in my opinion. I don't know how well the eshopps hang on works, but I know the in sump skimmer is excellent in my book so it could be worth looking at.