tl,dr: is it better to cut a sponge filter's lift tube, to cut the sponge, or to compress the sponge?
Hey guys, I bought a
from my LFS, because it was all that they carried, and I was eager to get started (and couldn't wait for an ATI Hydrosponge in the mail). Unfortunately, it's not possible to put an airstone into this particular unit, so the bubbles are large, make lots of noise, and splash a bunch.
I ended up taking the thing apart:
I removed all the 90 degree joint pieces, and tried to reconstruct what I thought the ATI sponges looked like.
I rain the air tube through the lift tube, and put an airstone on the end. In the "final version" (after I took pictures), I put a little cone over the airstone to channel all of the bubbles into the lift tube.
The airstone was inserted into the top of the sponge (remember that in the final version, there was a cone connecting the top of the sponge to the lift tube, with the airstone inside). But then I ran into my problem: It was too tall!
(left side of following pic)
[Color key: blue = water level/air line, red = lift tube/bubble cone, yellow = airstone, black = sponge, green = substrate]
So now my problem is: do I cut the lift tube down, thus reducing the flow/lift in the filter (furthest right in pic)? Or do I cut the sponge down, thus reducing the total surface area?
Right now, I've used the suction cups on the lift tube to squish the sponge at the bottom of the tank (middle in pic). Is this even a problem? The surface area should be the same for bacteria, but maybe since the compressed sponge would be denser, the water flux through the sponge would be reduced. Is there a way to check flow rate in these sponge filters?
What would you guys recommend doing?