The lifespan pf many of the more popular fish we commonly keep in the hobby can surprise many people.  Clownfish for example can commonly live up 15 years in captivity and many tangs can live up to 25 years.

http://www.int-res.com/articles/meps/134/m134p015.pdf

http://www.advancedaquarist.com/2009/12/fish2

Conscientious Marine Aquarist, 2008, Bob Fenner

Manufacture ratings should always be considered as guidelines and never hard fast rules.  In my opinion, almost all of these capacities are over rated.  The reason for my opinion is that manufactures typically complete their product testing with the gate valve and air valve(s) wide open to calculate the maximum flow rate and maximum air intake using these measurements to calculate the maximum rated capacity for the skimmer.  As we all know, the gate valve and air valve(s) will need to be adjusted in order for the skimmer to work properly which will also lower both the flow rate and air intake of the skimmer from the manufacture’s measurements.  This is why many hobbyist prefer to use skimmers that have a much higher rated maximum capacity than their aquarium.
The below link can help you determine how to pick out a skimmer for your set-up

https://www.reefaquarium.com/2013/selecting-a-new-skimmer/

And the below will offer you some other ways to evaluate potential skimmers

http://www.advancedaquarist.com/2010/1/aafeature

And some interesting skimmer information

http://reefbuilders.com/2012/12/20/protein-skimmers-function/

http://reefbuilders.com/?s=skimmers

If you are planning to use carbon dosing to reduce high levels of nitrates and/or phosphates, please keep in mind you need to start off slowly and at a very low level.  Making quick and drastic changes to your nitrate levels through all/any forms of carbon dosing will cause your water parameters to become at least somewhat unstable.  Take it very slow to begin with allowing your system to slowly adjust over time.   You have to always keep in mind, only bad things will happen fast in this hobby.

More information about carbon dosing can be found in the below article:

https://www.reefaquarium.com/2012/carbon-dosing-in-laymans-terms/

And a few other articles about carbon dosing

http://reefkeeping.com/issues/2008-08/nftt/

Sometimes you can thoroughly complete your research to ensure the best possibly compatibility between all of your fish, but you sometimes will just end up with all kinds of problems.  The reason for this is that fish can also have their very own unique and individual personalities.  And just like people, you can find miserable , grumpy, and mean fish that are completely different the average fish of the exact same species.  Although I would think this is a very small percentage, it is still a risk.
This is why I always recommend that you keep a very close eye on your aquarium every time you add a new fish to the set-up.  Even when you quarantine a new fish for 4 or 5 weeks, you may still not know with 100% certainty how well this will work out until you add them.

The below link and also offer a few guidelines to help you think through determining appropriate stocking for your aquarium
https://www.reefaquarium.com/2013/responsible-fish-keeping/

The below link can also offer you some good ideas about stocking butterflys in reef set-ups

http://reefbuilders.com/2013/10/29/keeping-butterflyfish-reefs-avoid/

Don’t underestimate the importance of waterchanges!

In may low demanding and more basic set-ups, weekly water changes in the range of 5% to 20% would be all that you would need to replace the consumed elements from your water as well as helping to control excesses nutrient build-up. Many people do not realize that water changes when cycling your tank can also be very important and beneficial with harming or prolonging most commonly used cycling processes.

Waterchanges when cycling a marine aquarium with at least some live rock my actually help you out down the road. This is very different from a typical fishless cycle in a freshwater aquarium. Within the nitrogen cycle that develops in your marine aquarium, you will develop bacteria that eats the proteins and turns them into ammonia.  This type of bacteria will reproduce a lot faster than the ammonia eating bacteria, so the ammonia produced can actually grow to toxic enough levels that will prolong the cycle. Typically this point occurs somewhere around 1 to 2 ppm of ammonia. This is why you have to do water changes if the ammonia reaches levels of 1 to 2 ppm or higher. The water change will help reduce the ammonia and other decaying particles from the tank helping the cycle complete faster and the water parameters become balanced quicker. Although there is some beneficial bacteria free floating in the water, it will be in such small amounts that water changes will not remove enough of them to be impactful in any way. This is why water changes when cycling with at least some live rock will help the cycle move along faster, not slow it down one bit.  This will also help to limit the potential for higher levels of nitrates before the nitrate eating bacteria has a change to develop which will reduce the risk of nitrate build up within your rock.

And the below are some more interesting article that I found and thought I would share

http://reefbuilders.com/2013/09/04/reef-octopus-nwb-sss-super-space-saver-brings-performance-smaller-package/

http://reefbuilders.com/2013/08/30/mini-flipper-algae-cleaner-brings-magnetic-flipping-action-smaller-tanks/

Beware of forums !!!

While forums are typically a great source of first hand knowledge, they can also be a pain in the backside for two different reasons.

When first starting and setting up your marine aquarium, your experience is limited.  Even when you research more than enough, you still can make a mistake here and their when you are new to the hobby.  Most of the time this is not a bad thing as there will be no permanent harm to your aquarium inhabitants and you will still be enjoying your aquarium in ignorant bliss, just like I had started started out in the hobby. However, if you unknowingly make a mistake to go to a forum to explain your situation and ask for advice, you will likely get a dozen or so people pointing out all of your mistakes.  This can make it real easy to feel bad about yourself and limit your enjoyment you will get from your aquarium.  Just keep in mind that almost all problems you will ever run into, can be corrected by applying a few basic and simple concepts.  This hobby is not a “Black Art”.

Another reason for this warning is some hobbyist who have many decades of experience can forget they are talking to a newer or lessor experience hobbyist at times.  This can make you feel like someone just explained to you how to build a watch when you only asked what time it was.  Don’t get down on yourself when this happens, and it will happen.  It can be easy to feel like you don’t know what you are doing when a fellow hobbyist tries to sum up his/her many many years of experience into a few paragraphs, just do your best to learn from the information.  Once again, stick to the basics doing those well, and most every thing else will fall into place.

Also, I thought I would share the below links as I found them very interesting and I hope you will as well

http://blog.aquanerd.com/2013/05/diablo-dc3500-controllable-pump.html

http://blog.aquanerd.com/2013/08/vertex-aquaristik-sump.html

http://blog.aquanerd.com/2013/09/picture-of-the-week-mccoskers-flasher-wrasse-paracheilinus-mccoskeri.html