slief
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You know UL, you could have a point in that opening the volute until the surge subsides is the key with that skimmer. I wish I had one to play with because I am sure I could find the sweet spot in a hurry. On the flip side, it's kind of funny to hear somebody say they would prefer less air in their skimmer. There are some that believe "he who has the most air wins" and are all hung up on how much air or scfh a skimmer is rated for. In my experience, you want as much air in the skimmer as possible (to a point). That point being where the skimmer starts responding for the worse or where you get bubbles that burst constantly at the surface.
In the case of this particular skimmer as well as others, surging is generally caused when there is so much water flow that the water can't exit the skimmer fast enough. The water height will raise creating head pressure inside the skimmer. There is a point at which that pressure will create a siphon out the effluent pipe of the skimmer. This causes the water level to drop fast. The cycle is then repeated which is why you see a constant up and down motion in the skimmer body that we refer to as surging. I've also seen this happen where something is directly in front of the effluent pipe on the skimmer such that it causes a bit of back pressure in the skimmer. Realizing that and also realizing that sump levels vary from one tank to the next, the adjustable volute becomes the tool of choice for balancing things out. Since this pump is constant rpm, opening the volute increases the air flow into the pump which in turn displaces some water with an equal amount of air, thus decreasing the amount of water entering the skimmer body while increasing the air.
Between sump level adjustments and volute adjustments is a sweet spot where you get a nice quality foam and a stable water/air mixture that doesn't produce much if any surging in the skimmer body. The nice quality foam is assuming you have enough DOC's which I will get to.
Reef_men, first off, welcome to Reef Central!!
A couple things come into play when installing a new skimmer. Reef_men, this one applies to you.. Give things a bit more time to settle in. A new skimmer (and you probably already know this) needs to build a slime coating up in the neck and body. We refer to this as breaking in. Until that happens (it can take up to two weeks) the body and neck will have more friction which can cause bubbles to pop prematurely or the bubbles may be larger than they will once the skimmer breaks in. During the break in period, adjustments to a minor degree will be a bit futile in that your fine tuning adjustments will really need to be made after the skimmer is completely broken in.
Having said, this is something I have mentioned in previous posts but I will reiterate it now. A skimmer needs proteins to create good foam. This is why they are called "protein skimmers" and this is a key ingredient to foam fractioning in a skimmer. These proteins are commonly referred to as DOC's or dissolved organic compounds. These DOC's are generated from waste like fish poop, uneaten food etc. It is why skimmers are rated for specific sized tanks and perceived loads. There are basic guidelines to minimum and maximum stock levels and good skimmer manufacturers like Royal Exclusiv rate the skimmer based on tank sizes due to perceived minimum and maximum stock loads. Royal Exclusiv is one of the few manufacturers that rates their skimmers honestly and conservatively where as many of the cheaper brands over rate them and tell you the skimmer is capable of larger volumes then they really are.
A skimmer is like a car or truck and needs a certain amount of fuel to operate and in the case of a skimmer, fuel comes in the form of DOC's. A smaller tank can only provide a small amount of DOC's where as a large tank can provide a large amount of DOC's. The end result is that if you place a really large skimmer on a really small tank, it will not work properly because there won't be enough protein or DOC's in the water for it to generate a good foam head. Instead what you will get are large bubbles that burst at the surface instead of a nice thick sticky foam where the bubbles stick together and overflow into the skimmer cup in a nice thick foam mess. If you have a well stocked tank and don't run a skimmer for a while and then set one up that is properly sized for the load, the skimmer will make some crazy foam for a while until it catches up with the waste and exports it in the form of skimmate. Then once it catches up, you would notice the bubbles or foam kind of change and the skimmate production slows down because there isn't enough waste in the water to keep up a great foam head or to keep the skimmer producing that nasty dark skimmate. With a properly sized skimmer, this is normal. Skimmate production will slow down but should remain consistent. With an oversized skimmer, this will be inconsistent. The skimmer will produce well for a short amount of time until the DOC's are reduced. Then it will idle along until the DOC's build back up at which point the skimmer will produce again and the cycle will repeat. Slow down, pick back up...
I only bring that up in case you guys or anybody happening upon this thread isn't aware of why the skimmer does what it does and what keeps them producing skimmate.
So reef_men, in your case, I suggest giving it a bit more time. You might consider raising the water level in your sump a tad but then again, you may be ok where you are at. Assuming your tank isn't brand new and assuming you have enough waste to feed the skimmer, you are going to have to find a balance between sump level and volute turns that not only creates stability inside the skimmer body but a balance that also produces decent skimmate assuming you have a decent amount of waste to feed it. Every tank is different. Salinity, DOC's, feeding habits, type of food being fed, even dissolved O2 or micro bubbles in the sump from the overlfow imact a skimmers performance. Oily foods such as mysis impact it as well just like placing your hands in the water. Those two can kill the skimmers foam in in a matter of seconds and it can take a couple hours or more depening the system volute for the skimmer to rebound.
I hope that helps. I monitor this thead constantly so I will keep an eye out for your posts. In the mean time, reef_men, how about a bit of info on your tank including display size, stock load and age of the system so I know a bit more and can better help you in the future.
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