There are 3 controls on a recirculating skimmer:
1. Input to the skimmer is controlled by gravity feed from the tank’s overflow with ball valve “or” a correctly rated feed pump that is matched to your skimmer.
2. Airflow is controlled by a air valve or air clamp. Any restriction to the air is controlling the air draw on the skimmer pump, even a smaller diameter air hose or connector inserted into the end skimmer pump’s air hose.
3. Output is controlled by wedgepipe, ball valve, or gate valve depending on the skimmer brand. Controlling the output also controls the water level within the skimmer.
To set the 3 controls on your recirculating skimmer correctly:
1. The first control is to adjust the water flow through rate through your skimmer. Typically, it is 1x to 2x turnover of your display tank, but each skimmer has an optimal range where it performs best. This is why it is so important to properly match your skimmer to your setup. For gravity feed, one would need to tailor the flow through rate back by a ball valve as described in control #1 above. The water turnover rate on your system from your return pump is usually much stronger than your skimmer can handle, typically 3x to 5x turnover of your display tank and you want only 1x to 2x turnover going through your skimmer. If not tailored back to the correct flow through rate, there will be too much turbulence within the skimmer and performance will be greatly affected. You can also feed skimmer with a correctly rated pump or powerhead, so no tailoring back is needed.
2. The next control is to restrict the air by tightening the air clamp or closing down the air valve and this piece was described above in control #2. What I’ve found when setting up a new skimmer is that the maximum air draw which yields the best foaming is not a fully open air hose, but restricting the air a little actually increases the air draw. I usually like to start with the air tailored back approximately 1/4 – 1/3 which usually yields the finest bubbles and good foamhead. As your skimmer breaks in, a fully open air tube would probably be your best performance. Each skimmer is different and also each hobbyist preference is wet or dry skimming is different. So, one sweet spot for one owner may not be for another.
3. The last control, after the water flow through rate and air have been adjusted correctly, is to adjust the water level within the skimmer. The starting point that I typically use is the the bubble breaking point just above the bottom of the collection cup. So, I like to start off at a lower bubble breaking level on new skimmers as the bubble breaking level tend to rise up as the skimmer breaks in. Also, with the skimmer pump turned off and with just the feed water flowing through the skimmer without any foaming, the water level should be within an inch of where the skimmer cup meets the skimmer body. For H&S and Deltec skimmers, start the bottom edge of the bayonet connection between the collection cup and skimmer body. If the water level is too low, tailor back the outflow from the skimmer drain with control device #3 as described above. Closing down the wedgepipe, ball valve or gate valve will raise the water level within the skimmer body. Also, for H&S skimmers only, the drain must not terminate underwater in the sump as this will affect performance. It is best to have the exhaust on the H&S skimmers terminate about 1/2″ above the sump water level. To quiet & reduce splashing, you can put a 45 or 90 degree elbow at the end of the drain pipe.
Once your skimmer is broken in and foaming, adjust wedgepipe to raise the water level and bubble breaking level for wetter skimming and lower for drier skimming.
I am a firm believer that a skimmer should be appropriately sized to fit the tank/bio load. Technology today is so advanced on skimmers that they have become very efficient in doing what they are supposed to do. Install a skimmer that is properly sized for your system or just a little oversized. I’ve never been one to endorse severely overkill on skimmers as I’ve seen and heard complaints about SOSS (severely oversized skimmer syndrome) where an overkill skimmer really doesn’t perform as well as a properly sized skimmer. So, you don’t want to undersize nor overkill. The mentality that “bigger is better” or “buy the biggest that you can afford” is not what we endorse. Another question that I get a lot is should I run my skimmer 24/7. Yes.