Fist things first. After I pulled the skimmer back out of the sump, I decided to bore out the venturi so more air could be sucked into the skimmer. Pretty easy to do as seen here:
Now, this is probably the most popular modification people do to their ASM skimmers. It is called the recirculation mod. I fist read about it at www.asmskimmer.com . It is an incredibly simple way to juristically increase the performance of the skimmer. A stock needle wheel skimmer sucks water in from the sump with the main skimmer pump (the needle wheel) and the water gets processed once before it gets blown out of the exhaust tube. A recirculating needle wheel skimmer sucks water in from the bottom of the skimmer and shoots it right back in so the same water gets processed over and over which increases the dwell time (time the water stays mixed with the air) and thus the amount of sludge the skimmer can take our of the water.
The modification itself is fairly simple, but you’ve only got one shot at it or you ruin your skimmer. I simply turned the pump so the venturi was positioned up against the skimmer body, then I used a dermal to cut a hole in the skimmer body so the venturi could stick in. I also replaced the elbow that came with the pump and fed the skimmer with 1” PVC because the stock elbow was not long enough.
Next, I had to make the new hole for the venturi water tight (or as close to it as I could. Its an in sump skimmer thank goodness, so its not all that important). At asmskimmer.com they use rubber seals called uniseals, which are basically flexible rubber bulkheads. If you can get your hands on one of them, it would be best, but I couldn’t fine them around here for the life of me, so I improvised. I took a 1” PVC coupling, and cut it in half. I then worked it on the belt sander to fit the outside of the skimmer body exactly. I used regular PVC glue to stick it to the skimmer body accept the venturi, and it worked perfectly.
Of course, on a recirculating skimmer, the needle wheel pump re-circulates the water, not feeds the skimmer, so another method has to be used to get the water from the sump into the skimmer to be processed. For this I took a ¾” male thread by ½” barb elbow fitting and cut a hole for it in the skimmer body. On the inside of the skimmer I glued (again after working it on the belt sander to match the contours of the inside of the skimmer) a ¾” female thread by ¾” barb elbow to accept the outside elbow fitting. I could now attach this fitting to ½” vinyl tube to feed the skimmer.
Some people use small submersible pumps or a power head to feed the skimmer, but I wanted to feed it directly off the drain line from the main display tank. This is a great way of doing it because it doesn’t require another pump (which cost money and use energy) and it allows the nutrient rich water off of the surface of the display to be directly processed by the skimmer. Here’s a pic of the set up I used to run a tube of the drain line.
the vinyl tube runs to the skimmer while the 1 ½” PVC takes care of whatever water is left.
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