Hi there. Not sure which forum to ask these questions in, so I will do so here.

I have a hang-on-the-back filter for my 125litre tank, (will be adding another soon)



1. The filter pads (marked in blue) Would it be better to remove these, and fill in the space left with K1 media? Also maybe cut back the sponge a little to create more space for the K1? (possibly adding an air supply into the space to increase movement of the K1 aswell)

2. Would the filter perform better, if I removed some of the plastic (marked in red) exposing more of the sponge?

Any other advice on increasing the efficiency of this filter would be appreciated

I wouldn't cut the plastic. this will actually have the reverse effect making your filter less efficient. the water will flow through the sponge faster but it will be flowing through less of the sponge. I am not familiar with K1 media so i can't really say anything about using it

Ok, I understand what you mean about cutting the plastic. I should have realised that myself....

The reason I asked about the K1 media is because from what I have seen in various videos I have watched, it seems to be very popular for growing healthy bacteria. I figured it would work better than those pads I have in there. (The filter was pretty cheap, so im guessing those pads wont do much to improve the water anyway...)

Ok heres what I have done.



I've cut the filter sponges back by about 1cm, and used this to pack the center. This way I have created more space in the side areas, but not lost any sponge filter area.

When my K1 media arrives, I will be removing the white pads, and filling the area marked red, with the media.

I will also be drilling a small hole in the bottom of each side and adding an air line, to provide the K1 media with the oxygen and movement it needs to work properly.
Hopefully this will greatly increase the efficiency of these filters.

Heres what my tank looks like right now.



Does it look like it could use another water change? Or does it look ok now?