Skimmer VS. Filter VS. Sump

What's really necessary and what's the advantages and disadvantages of one over another? From what I've heard and read, only one is really necessary.

 

They do not perform the same functions. Start here.

http://www.3reef.com/forums/reef-aquarium-articles-how-tos/all-about-sumps-filters-fuges-79852.html

 

And for skimmers start here: http://www.3reef.com/forums/protein-skimmers/all-about-skimmers-skimmers-skimmer-85389.html

 

Actually, none are really necessary if you do water changes everyday which is next to impossible. But even with all the equipment mentioned, water changes are still necessary.

IMO, a skimmer is the most important component, it is the heart if any marine tank. If you have enough live rock and flow in the DT for bio-filtration/dissolving organic compounds then the skimmer will come behind and remove dissolved organics. Also a skimmer oxygenates the water.

Sumps are great and highly recomended IMO because they offer a place for equipment, increase the water volume and can be fitted with a refugium where Isopods, amphipods, Copepods, and bristleworms can do their jobs unpredated. They can also be home to mangroves, deep sandbeds where anarobic bacterie can denitrify, or lots more live rock.
Also, when a sump us kept on a reverse light cycle it helps reduce pH swings between day and night.

Hope this little bit helps

 

Oh, you can also use a sump for holding chemical filtration like carbon or Chemi-pure

 

They all do their own parts but if you have to choose just 1 get the best skimmer for your size tank that you can (just be aware that that may also necessitate the addition of a sump to operate the skimmer in)

Isn't this hobby fun? full of built in justifications for upgrades

 

+1 on a skimmer being the most essential of those 3. A sump is a huge convenience and makes the tank look better aesthetically also. It also increases the capacity of your tank among many other benefits. But you can succesfully have a SW tank without one.

A filter IMO will just become a nuisance as it traps debris and raises your Nitrate, I don't see a huge need for filters in SW keeping. The consistent maintenence of them would just be counterproductive.