Defusing A HOB Filters Current
By Ivan M. Shaw (Zoban)

HOB Filters or Hang On Back Filters typically have a 'waterfall-outlet,' where the water falls down out of the filter into the tank. The obvious problem is that as the water falls from the outlet, it accelerates under the force of gravity until it reaches the waterline, then creating a strong current.

The secret to stopping the current is to simply obstruct it.

Materials:
-Empty 2L Soda Bottle (well rinsed)
-Pair of Scissors
-Masking Tape (or other with strong hold)
-Tape Measure (optional for neatness)
-Marker (optional for neatness)

Step 1:

Measure the distance across the water outflow, in the case used here it is 5" across.

Step 2:

Cut the bottom off the bottle along the seam/edge made with the flat label area.

Step 3:

With the Marker draw a straight line up the label area beside the Glue left from the label.

Step 4:

Using the Tape Measure lock it in place just over the length from above I used 5 ^1/4" in this case. Holding the tape in place as shown, turn the bottle and mark a dashed line you can follow with scissors

Step 5:

Now we cut the line drawn in Step 3 and the dashed line in Step 4. To make it easier to cut the dashed line you may wish to cut the upright into the funnel portion of the top and rough cut around the top before trying to cut the dashed line.

Step 6:

At this point we have one long piece of plastic that is curled up. For my implementation I had two of the HOBs that I wanted defused so I cut the curl in half after removing the 1" wide glue area.

Step 7:

Now we position the curl over the water outlet and tape it in place as shown.

Finished:

Here is a picture from the side to show how it curls under the waterfall to defuse the current created and from the front to illustrate it's stealth.

You know it took me longer to type this then to make and install two of these.