In a brand new tank you probably will get nothing. Nada. Zip.
In a tank a few months on, yes. You will get skimmate if you have a good skimmer. In a nano, not so much problem with nitrate: water changes generally keep up with it. The bigger the tank, the bigger the skimmer needs to be...and the more efficient it needs to be. Can you run without one? Well, fish will get along. The water would be nicer if you had one, but fish do survive high nitrate that would do in corals. Where do corals like it to be? About 5 for, say, frogspawn stony. Corals continually cycle water through and suck up nutrients and minerals, and the stonier they are, the less they appreciate nitrate and too-rich water. Softies can get by, but by the time you get to the fussy sps, the colored sticks, they do NOT like it.
Ideally, a good skimmer for a reef should produce a meringue-like foam that will stand on its own...as this tops the rim of the collection cup it dissolves into mucky stuff. This is what's leaving your tank. Cone-type skimmers are good at the stiff foam production. Those that produce a little froth are not as efficient.
You think your water is clear? A skimmer may pull out near-black goo from it...amino acids, residue from biology going on. Skimmate ranges from the color of weak tea to nasty smelling ooze and green-black soup---and what a skimmer pulls out is largely dependent on the foam it produces.
It's what the ocean does when it makes foam. Beaches are the ocean's collection cup, so to speak. There are instances where it piles up and up head-high. Why? Dunno---but something large may have died.
Tricks with skimmers: the skimmer can be bought used: they don't wear out---their pumps can be replaced. A brand new one may need to be wiped down with white vinegar, to cut the oil that may attend the molding process.
And if you put your hands into the tank your hand cream besides not being good for the fish and corals at ALL can send your skimmer into a 3-day tizzy in which it vomits brown water and foam all over your sump. Just adjust its air flow (there is an adjustment) so it won't overflow every 3 minutes, and watch your salinity! if you're emptying that cup a lot, you're losing salt water and your autotopoff is pouring fresh water in!
Is an in-sump better than a hang-on? Generally yes for one reason: skimmers CAN overflow. If one does (some brands do this on startup after a power out) you do NOT want it doing it outside the sump.
Say you're going on vacation? It's better to have the skimmer shut down for a few days than to come back to a foamy mess. Your tank will probably get along better with that situation. Few tanksitters are going to volunteer to clean a skimmer cup, and fewer than that probably will succeed in getting it properly seated. A tank will not die of a week or so of no skimming. It will play catchup when you get back and turn it on.
Hope that clears up some confusion. I personally recommend a cone-style skimmer for any reef 50 gallons and above. Good ones ARE expensive, but I rank it up there with good lights and good circulation when it comes to reefing.
In a tank a few months on, yes. You will get skimmate if you have a good skimmer. In a nano, not so much problem with nitrate: water changes generally keep up with it. The bigger the tank, the bigger the skimmer needs to be...and the more efficient it needs to be. Can you run without one? Well, fish will get along. The water would be nicer if you had one, but fish do survive high nitrate that would do in corals. Where do corals like it to be? About 5 for, say, frogspawn stony. Corals continually cycle water through and suck up nutrients and minerals, and the stonier they are, the less they appreciate nitrate and too-rich water. Softies can get by, but by the time you get to the fussy sps, the colored sticks, they do NOT like it.
Ideally, a good skimmer for a reef should produce a meringue-like foam that will stand on its own...as this tops the rim of the collection cup it dissolves into mucky stuff. This is what's leaving your tank. Cone-type skimmers are good at the stiff foam production. Those that produce a little froth are not as efficient.
You think your water is clear? A skimmer may pull out near-black goo from it...amino acids, residue from biology going on. Skimmate ranges from the color of weak tea to nasty smelling ooze and green-black soup---and what a skimmer pulls out is largely dependent on the foam it produces.
It's what the ocean does when it makes foam. Beaches are the ocean's collection cup, so to speak. There are instances where it piles up and up head-high. Why? Dunno---but something large may have died.
Tricks with skimmers: the skimmer can be bought used: they don't wear out---their pumps can be replaced. A brand new one may need to be wiped down with white vinegar, to cut the oil that may attend the molding process.
And if you put your hands into the tank your hand cream besides not being good for the fish and corals at ALL can send your skimmer into a 3-day tizzy in which it vomits brown water and foam all over your sump. Just adjust its air flow (there is an adjustment) so it won't overflow every 3 minutes, and watch your salinity! if you're emptying that cup a lot, you're losing salt water and your autotopoff is pouring fresh water in!
Is an in-sump better than a hang-on? Generally yes for one reason: skimmers CAN overflow. If one does (some brands do this on startup after a power out) you do NOT want it doing it outside the sump.
Say you're going on vacation? It's better to have the skimmer shut down for a few days than to come back to a foamy mess. Your tank will probably get along better with that situation. Few tanksitters are going to volunteer to clean a skimmer cup, and fewer than that probably will succeed in getting it properly seated. A tank will not die of a week or so of no skimming. It will play catchup when you get back and turn it on.
Hope that clears up some confusion. I personally recommend a cone-style skimmer for any reef 50 gallons and above. Good ones ARE expensive, but I rank it up there with good lights and good circulation when it comes to reefing.
but I do get a light coffee color concoction that is aromatic to say the least. 
