Sponge Filter Dominance
Sponge filters provide biological filtration without sucking in fry. Pore size is too small for fry to enter.
Bacterial colony seeds faster than most other filter media.
Cost is under $5 per unit and they last years.
When to Upgrade to HOB
Week 6 onwards, fry are typically too large to get sucked into HOB intakes.
Cover HOB intake with a pre-filter sponge for extra safety.
HOB adds mechanical filtration and surface agitation sponge alone lacks.
When Canister Makes Sense
Large grow-out tanks (40+ gallons) with 200+ fry need canister capacity.
Always use pre-filter sponges on canister intakes.
Sponge Filter Setup Tips
Seed sponges in an established tank for 2 weeks before moving to the fry tank — instant biological capacity.
Squeeze sponges gently weekly in tank water (never tap water) to discharge debris.