Hang-On-Back (HOB)
Cheap, easy to clean, fits most tanks.
Mechanical + biological filtration in one unit.
Best for 10 to 55 gallon community tanks.
Canister
Sealed external unit with high volume media.
Quiet and powerful. Handles 50+ gallon tanks with ease.
Expensive, complex to clean, but gold standard for medium-large tanks.
Sponge
Cheap, simple, ideal for fry tanks and quarantine.
Air pump required. Low flow, low disturbance, gentle on small fish.
Not ideal as primary for heavily stocked display tanks.
Internal
Submerged unit inside tank.
Good for small tanks or secondary filtration in medium tanks.
Takes up visual space.
Sump
Reserved for saltwater and large freshwater setups.
Hidden second tank under main tank houses filter media and equipment.
Expert setup, expert results.