IN MY OPINION AND EXPERIENCE
Nick, understand the basics of a reef aquarium. What wastes you put in must come out if you are to keep a clean healthy reef. A skimmer directly removes wastes in a tank before they have a chance to further break down further and pollute your system. Therefore, you can't skim too much (only a putz would argue this point

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Growing macro algae in a refuge, or relying on a sandbed or other biological filtration is a poor option. Yes these methods will work to some extent but you could easily remove much more wastes with a quality skimmer...........and you don't have to make separate contraptions or have additional tanks with lights to grow macro algae..
Lots of skimmer companies will have ridiculous rating for their skimmer, saying their skimmers will skim tank up to 100, 200, or 300gal tanks. In all reality most of these skimmers won't handle a 40 gallon tank with a light bioload. Why do they have these ratings? Because they can. No one has scientifically disproved their ratings, although user experiences have proved them to be inadequate.
When looking at a skimmer take a look as the amount of air it produces. This will be your best gauge to determine it ability to handle a tank size.
IME a good formula for a minimum amount of air a skimmer should produce to aquarium size is 1 LMP (liter of air per minute) 60 LPH (per hour) for 10 gallons of tank water. Granted, you will not get this info on a lot of skimmers out there, most quality ones will have this info handy.
ANYWAY, For $100 you will not find anything that will handle your system (new) but a used remora skimmer will remove some crud. Good luck!