Its probably worth elaborating a little on why skimmers can be such an essential part of any reef set up.
There is no more effective way of saturating the aquarium water with dissolved gases. Without a skimmmer the only way gases are going to get into the tank to be used by the inhabitants is via the surface. Aquariums have a tiny surface are compared to any natural habitat. Airstones are OK for a short while but soon a scum will be noticed forming where the bubbles reach the surface. Unless this is removed it will inevitably add to the organic load of the habitat. No airstone is anywhere near as effective at maximising the amount of gas to be dissolved into the water as a counter-current skimmer.
Unless a mature, balanced and healthy deep sand bed within a refugium is being used it is almost impossible to maintain a healthy reef tank without a skimmer unless almost constant water changes are carried out. Even then the jury is still undecided - there have been a number of dismal failures recorded with deep sand bed techniques.
There is no more effective way of removing soluble organic waste. The key word here is remove. All that most filters will do is carry out some part of the nitrogen cycle - almost always raising the nitrate level. Anaerobic nitrate removers are tricky to maintain and have never really caught on.
Skimmers, if operated correctly, produce surprising amounts of brown sludge from otherwise pristine looking aquariums. This foul muck would otherwise be left in the tank for the overloaded filter to deal with.