I initially voted 3-4. But when I started typing I realised I should of voted the 11+ ways. Maybe an overkill on my behalf.
Clarisea Filter
Nyos Skimmer
Tunze Algae Reactor
Seachem Matrix Carbon
GFO
Aqua Forest Bio Fil
Marine Pure Blocks
Aqua Medic UV Sterilizer
Carbon
CO2 Scrubber
Aqua Forest Bio S Pro
Clarisea Filter
Nyos Skimmer
Tunze Algae Reactor
Seachem Matrix Carbon
GFO
Aqua Forest Bio Fil
Marine Pure Blocks
Aqua Medic UV Sterilizer
Carbon
CO2 Scrubber
Aqua Forest Bio S Pro