AquaEL 500 filter UV

http://www.aquatics-warehouse.co.uk/acatalog/AquaEL_500_filter_UV.html

Fluval Plus Internal Underwater Filter Plus Series

http://www.seapets.co.uk/products/aquarium-supplies/fish-tank-equipment/aquarium-filters/internal-power-filters/fluval-plus-underwater-filter-model-3.html?ref=googlebase

Eheim 2180 Professional 3 Thermo Filter

http://www.charterhouse-aquatics.co.uk/catalog/eheim-2180-professional-thermo-filter-p-1052.html

Bio System Power Filter & Oxy Surface Skimmer

http://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=16729

http://www.aquaticcommunity.com/review/showproduct.php?product=354&cat=4

Eheim Aquaball 180 Internal Filter

http://www.charterhouse-aquatics.co.uk/catalog/eheim-aquaball-180-internal-filter-p-1110.html

Penn-plax Cascade 700 External Filter for aquariums up to 300 litres

http://www.rocketaquatics.co.uk/pennplax-cascade-external-filter-aquariums-litres-p-143.html

Fluval G3 Power Filter

http://www.seapets.co.uk/products/aquarium-supplies/fish-tank-equipment/aquarium-filters/fluval-g-power-filters/fluval-g3-power-filter.html

The Under Gravel Filter Controversy (article)

http://www.firsttankguide.net/ugfcontroversy.php

Top 5 Power Filters (article)

http://freshaquarium.about.com/od/toppicksfilters/tp/powerfilter.htm

Eheim - Aquaball 45 internal filter

http://www.currentsea.com/search.php?search_item=gal

http://www.fishandfins.co.uk/eheim-aquaball.htm

Tom Pro Series filters

http://www.aquatichouse.com/FILTRATION%20MENU_files/tomwetdry.asp