equipment
Sponge filter vs hang-on-back filter
Which filter suits a small to medium tank?
Short answer
A sponge filter is gentler, safer for fry and shrimp, and cheaper. A hang-on-back moves more water, gives better surface agitation and takes chemical media. The choice usually follows from what is in the tank.
Side by side
| Dimension | Sponge filter | Hang-on-back filter | Favours |
|---|---|---|---|
| Flow rate | Low | Moderate to high | Hang-on-back filter |
| Intake hazard to fry and shrimp | None | Real, unless a pre-filter sponge is fitted | Sponge filter |
| Surface agitation | Modest, via bubbles | Good, via the return | Hang-on-back filter |
| Chemical media | Not without modification | Yes | Hang-on-back filter |
| Noise | Air pump hum and bubbles | Water noise as the level drops | — |
| Cost | Very low | Low | Sponge filter |
| Visible in the tank | Yes | No, hangs on the rim | Hang-on-back filter |
| Suits a betta or blackwater tank | Yes | Only with the flow baffled | Sponge filter |
Which to choose
Sponge filter
Choose a sponge filter for shrimp tanks, fry tanks, quarantine tanks, bettas and anything needing very gentle flow.
Hang-on-back filter
Choose a hang-on-back for a general community tank where you want easy servicing and stronger circulation.
One caveat
They are not exclusive. A sponge filter running alongside a hang-on-back gives you a permanently cycled spare filter for a quarantine tank at almost no cost.