I think I need more anaerobic bacteria in my tank ....

• I have 2 YO DSB 55G tank
• Constant 40 PPM No3
• Been dosing NoPox for the last 2 months or so
• Thinking of replacing my pile of LRs in the sump with Seachem Matrix Media

So my question is:

1. Do you think it's efficient to put Matrix in media bag in overflow chamber in the sump?
2. So no reactor nor cannister filter due to sump size restriction ...

I dose 6 ml of NoPox on nightly basis but Nitrate has been steady at 40 ppm so I'm thinking of enlarging the media for anaerobic bacterias to live in .. hence the thinking of putting Seachem Matrix into my 55g tank.