I have been running skimmer (AquaC EV120) before I switch to only TAF for a year plus. Tried running only TAF since Nov 2008 until last week (total 408days) and I found that my tank has lots of tube worms growing on the sandbed, LR and even on the glass. However, just added a Deltec APF600 last week to run together with my TAF.
IMO, TAF operates differently with skimmer, its all depends on what your want:
Skimmer – Design to remove the DOC from the tank water before it degrade to NO3 and PO4 which TAF is unable to remove.
TAF – The algae grow naturally will absorb the NO3 and PO4 in the tank water but the water will remain full of DOC (or dirt).
TAF:
Adv: Preserve food for coral and all micro organisms in the tank.
Adv: Absorb NO3 and PO4 from tank water and export when cleaning.
Adv: Cheap and easy to setup.
Disadv: Will left lots of dirt in the tank.
Disadv: Need to clean the algae periodically, if not the algae die off will release the NO3 and PO4 back to tank
Skimmer:
Adv: Provide more surface for water and air surface thus tank water is more oxygen rich.
Adv: Remove DOC and dirt from tank. Hence tank is cleaner than only TAF.
Adv: Cleaning is easier than TAF.
Disadv: Unable to remove NO3 and PO4 from tank.
Disadv: The initial investment will be high to have an efficient skimmer.
From what I have observed:
Both TAF and skimmer will increase the temp in tank. TAF is from the light and Skimmer from pump
Both need periodic cleaning.
Both also consuming almost equal amount of power. Light and Pump.
As I mentioned, currently I am using both TAF and Skimmer with running independently. TAF on18hr/off6hrs and skimmer is 24hrs. Never test the NO3 yet but I did test the NO3 while I am only running TAF with salifert testkit. My NO3 can achieve < 5ppm without skimmer and WC for > 6 months.