Over the past couple years, I've accumulated a whole bunch of sponge filters. I like the Hydro line for quality, longevity, consistency and interchangeability. But they are hard to get new, and not the cheapest. So a few off-brand types have showed up in my collection.
One of the earliest purchases was the Powkoo dual sponge filters. I've learned two tricks recently to get these performing really well for me, so I thought I'd share.
The first is to set the height of the outflow elbow at the top of the unit right at the water line. If the head of the uplift tube is much below the surface, the bubbles come up the tube vertically, exit the elbow horizontally, then immediately continue upwards to the surface. This pulls or drags the water coming up the tube along a similarly zig-zag vector. But, with the open end of the elbow half out of the water, the bubbles exit the elbow with good velocity, and they don't have to 'pull' the moving water any higher than that. It also means that the water being pulled up the tube continues horizontally across the surface of the water with much greater flow and velocity. The first vid linked below shows this really well.
The second discovery is that the internal workings of the hard plastic structure, right where the airline gets plugged in, includes a jetlifter type of design. When these 'slots' are properly cleaned out (and nowhere does it say how to do this), the uplift is really really good. But because the slots for air to exit the 'baffle' and enter the main uplift are very fine and have hard edges, they catch debris easily, meaning they clog easily and flow becomes really limited. The before and after performance after I cleaned this part out with a pipe brush was night and day. A trickle of bubbles and barely any water movement turned into awesome performance, with nice horizontal flow from the top. I've included a few pics and youtube links (my vids) to show all this.
I have checked a few other brands (non-brands) of dual sponges, and they all seem to be trying to do the same thing, ie aim to function like a jetlifter.
Cheers!
Youtube vids:
https://youtu.be/u4_YrIdYRjU
https://youtu.be/ssIXUXlN8Fo - this vid shows the bubbles coming out of the housing and starting up the uplift tube in a sort of ring around the outside of the tube, due to the slots or whatever where the bottom of the tube seats into the black plastic housing (see first pic).