How to Choose the Right Aquarium Filter (HOB, Canister and Sponge)
By Melbourne Tropical Team ยท 2 min read
The filter is the heart of your aquarium. Here is how the main types compare and how to pick and size the right one for your tank.
What a filter actually does
A filter does three jobs: mechanical (traps debris), biological (houses the beneficial bacteria that process toxic ammonia and nitrite) and chemical (optional media like carbon). The biological job is the most important - which is why you should never clean all your media in tap water at once.
The main filter types
Sponge filters - cheap, simple, air-driven, gentle flow. Brilliant for shrimp tanks, fry, hospital tanks and bettas. Hang-on-back (HOB) - easy and affordable, hangs on the rim, great for small to medium community tanks. Canister filters - powerful external units with lots of media, ideal for larger or heavily stocked tanks and planted aquascapes. Internal filters - compact all-in-one units for smaller tanks.
How to size your filter
Look at the flow rate (litres per hour). As a rough guide, aim for the filter to turn over the tank volume about 4 times an hour for lightly stocked or planted tanks, 6 times for a typical community, and 8-10+ times for messy or heavily stocked tanks. Remember rated flow drops once media is added, so size up rather than down. Our filter flow calculator works out the turnover for you.
Filter tips
Bigger filtration is almost always better. Rinse media gently in old tank water, never tap water, and never replace all the media at once or you will lose your bacteria and trigger a mini-cycle. Match the flow to your fish - bettas and gentle species dislike strong current, while rivers fish and goldfish love it.