The object of a skimmer is to produce what surf does. Sea foam. Occasionally you will see news articles where a storm has whipped up a regular meringue of foam on a beach---taller than a man, spread in great drifts along the beach. You'll see pix of children and grownups playing in this froth.
And you'll shudder, if you're a marine hobbyist. What you have there is fish poo, fish spit and coral spit. And rot. Lots of it. Nitrate level in that lovely foam is probably, well, high.
Since we don't have tides and surf in our tanks, we found a way to generate bubbles and froth another way, by injecting air into a water stream. Skimmers have various ways of doing this, with varying degrees of efficiency, and HOW efficient they are determines how happy corals are. And fish. The froth is amino acids, which can break down into nitrate, as this chemistry bonehead somewhat understands it. And while a smidge of it is good (corals like SOME nutrient) a lot of it in your water is not good.
Softie corals can take fairly 'rich' water. LPS (hammer, candycane stonies, etc) can take moderately rich water. SPS (the colored sticks and encrusting stony like monti) can't.
Your skimmer makes the difference in the average instance. The better the skimmer the fussier the coral you can grow. [Light spectrum and flow are also very important, again softies at the tolerant end of lowness---and sps the most demanding.]
Your skimmer also is your emergency-fixer. If you've got a water quality issue, eg, if you're doing a lights-out to fix red slime, you need that skimmer working to take OUT the die-off. [Water changes help, too.] If you've used something that says---skim afterward---they mean skim. Or do water changes. Skimming isn't a sub for water changes: would that it were---but it can't replace lost nutrients. So those are still required; but water changes are also a way to transport an oversupply of something bad OUT of your tank. If you have a weak skimmer--don't run low on your salt supply, because water changes are your compensation.
Now: types:
Bubbles. The earliest type of skimmer probably is the type that sucks air into a chamber and makes a lot of bubbles, which can be dialed up and down. There's no little airhose on this type, and they're good for a softie tank, but they don't handle a very big tank. 70 gallons is about their limit, maybe a bit more, backed by faithful water changes and good sand management.
Venturi. This uses an airline to the surface to create more bubbles than the simple injection can. The airline feeds to the pump, which produces a cloud of bubbles. More efficient than the plain injection type.
Cone skimmers...not sure how to describe these, except that they have a tower narrow at the top and a foam-making chamber. They use a column of foam to assure a lot of bubbles rise. They're more efficient as a type, but if they say 'must sit in 5.5 inches of water', they mean it. You can build a platform in the sump to make that happen.
You have to keep the surfaces in your skimmer clean to let it function well. You also will not get good action out of a skimmer 1)when it is new, because it has fine oils on it from the plastic-forming process. A wipe-down with white vinegar can help remove this and hasten it into action. 2) when your tank is new, obvious reason---your water is pure, with very little amino acids or nitrate in it. Which is why new tanks often have a 'honeymoon' with coral and then head downhill in a handbasket. Do you see why? The way to prevent this 'coral crash' is to HAVE enough skimmer to ramp up and handle the future problem.
What a skimmer produces is skimmate. Nasty, often smelly, dark. Allowing more water to dilute the skimmate means filling the cup often, tossing often, and a skimmate that is more pale brown...is what is called skimming 'wet'. Sometimes when you want to remove something from the water in a hurry, you skim 'wet.'
Tuning a skimmer means standing there and turning the little knob until you have a real good bubble production, but so that the froth is not surging up in the tower to immediately flood the cup. It's a balancing act. It takes time. Don't just plug it in and walk away: that invites a flood. Make it so it takes at least a day to fill that cup or you will have an over-flood.
Likewise---you will see skimmer bubbles stop if you a) put your hands in the tank (our skin oils) or b) if you've just fed. Do not touch that dial! The skimmer will resume function as soon as it can. Adjusting it can only mess things up.
A good rule of thumb, particularly on the less efficient types of skimmers, is to buy a skimmer rated for 2x your system water volume. As the efficiency of the skimmer goes up, this is less true, but not entirely. Overshoot, rather than undershoot: gauge your bio-load and buy accordingly.
Hope this at least gives you an overview of managing these things: they're pricey, and, with lights and pumps, THE most important piece of equipment you'll buy.
And you'll shudder, if you're a marine hobbyist. What you have there is fish poo, fish spit and coral spit. And rot. Lots of it. Nitrate level in that lovely foam is probably, well, high.
Since we don't have tides and surf in our tanks, we found a way to generate bubbles and froth another way, by injecting air into a water stream. Skimmers have various ways of doing this, with varying degrees of efficiency, and HOW efficient they are determines how happy corals are. And fish. The froth is amino acids, which can break down into nitrate, as this chemistry bonehead somewhat understands it. And while a smidge of it is good (corals like SOME nutrient) a lot of it in your water is not good.
Softie corals can take fairly 'rich' water. LPS (hammer, candycane stonies, etc) can take moderately rich water. SPS (the colored sticks and encrusting stony like monti) can't.
Your skimmer makes the difference in the average instance. The better the skimmer the fussier the coral you can grow. [Light spectrum and flow are also very important, again softies at the tolerant end of lowness---and sps the most demanding.]
Your skimmer also is your emergency-fixer. If you've got a water quality issue, eg, if you're doing a lights-out to fix red slime, you need that skimmer working to take OUT the die-off. [Water changes help, too.] If you've used something that says---skim afterward---they mean skim. Or do water changes. Skimming isn't a sub for water changes: would that it were---but it can't replace lost nutrients. So those are still required; but water changes are also a way to transport an oversupply of something bad OUT of your tank. If you have a weak skimmer--don't run low on your salt supply, because water changes are your compensation.
Now: types:
Bubbles. The earliest type of skimmer probably is the type that sucks air into a chamber and makes a lot of bubbles, which can be dialed up and down. There's no little airhose on this type, and they're good for a softie tank, but they don't handle a very big tank. 70 gallons is about their limit, maybe a bit more, backed by faithful water changes and good sand management.
Venturi. This uses an airline to the surface to create more bubbles than the simple injection can. The airline feeds to the pump, which produces a cloud of bubbles. More efficient than the plain injection type.
Cone skimmers...not sure how to describe these, except that they have a tower narrow at the top and a foam-making chamber. They use a column of foam to assure a lot of bubbles rise. They're more efficient as a type, but if they say 'must sit in 5.5 inches of water', they mean it. You can build a platform in the sump to make that happen.
You have to keep the surfaces in your skimmer clean to let it function well. You also will not get good action out of a skimmer 1)when it is new, because it has fine oils on it from the plastic-forming process. A wipe-down with white vinegar can help remove this and hasten it into action. 2) when your tank is new, obvious reason---your water is pure, with very little amino acids or nitrate in it. Which is why new tanks often have a 'honeymoon' with coral and then head downhill in a handbasket. Do you see why? The way to prevent this 'coral crash' is to HAVE enough skimmer to ramp up and handle the future problem.
What a skimmer produces is skimmate. Nasty, often smelly, dark. Allowing more water to dilute the skimmate means filling the cup often, tossing often, and a skimmate that is more pale brown...is what is called skimming 'wet'. Sometimes when you want to remove something from the water in a hurry, you skim 'wet.'
Tuning a skimmer means standing there and turning the little knob until you have a real good bubble production, but so that the froth is not surging up in the tower to immediately flood the cup. It's a balancing act. It takes time. Don't just plug it in and walk away: that invites a flood. Make it so it takes at least a day to fill that cup or you will have an over-flood.
Likewise---you will see skimmer bubbles stop if you a) put your hands in the tank (our skin oils) or b) if you've just fed. Do not touch that dial! The skimmer will resume function as soon as it can. Adjusting it can only mess things up.
A good rule of thumb, particularly on the less efficient types of skimmers, is to buy a skimmer rated for 2x your system water volume. As the efficiency of the skimmer goes up, this is less true, but not entirely. Overshoot, rather than undershoot: gauge your bio-load and buy accordingly.
Hope this at least gives you an overview of managing these things: they're pricey, and, with lights and pumps, THE most important piece of equipment you'll buy.
