Resun medium-pore sponge 35 ppi, 10×15 cm is a filter media made of black foam in the shape of a cylinder. It is used as media for external canister and internal box filters and with a pump head. The sponge provides mechanical filtration — it traps suspended debris — and biological filtration: beneficial bacteria settle on its porous surface and break down harmful substances. The manufacturer rates its service life at over a year. It should be cleaned as it gets dirty, without detergents — just squeeze it out under running water.
What 35 ppi means
PPI stands for pores per inch. The higher the number, the finer the pores and the finer the debris the sponge traps, but the faster it clogs. A 35 ppi sponge is medium-pore: it catches visible dirt and food leftovers well, does not clog quickly and gives bacteria a large surface. That is why such a sponge is often the main stage of a filter, with fine filter floss added for "polishing" the water.
Key specifications
| Parameter | Value |
|---|---|
| Type | filter sponge |
| Pore size | 35 ppi, medium |
| Shape and size | cylinder 10×15 cm |
| Material | foam |
| Colour | black |
| Filtration | mechanical and biological |
| Service life | over 1 year |
| Filters | external, internal, pump with sponge |
Pros
- Versatile pore size. 35 ppi balances filtration and time before clogging.
- Mechanical and biological. Traps dirt and houses bacteria.
- Long-lasting. Over a year with proper care.
- Easy to clean. Squeeze under water, no chemicals.
- Fits various filters. External, internal and pumps.
- Can be trimmed. The foam is easy to cut to size with scissors.
Cons and what to watch
- Inaccuracy in the description. It calls the bacteria on the sponge anaerobic; in a flow-through filter it is mainly aerobic nitrifying bacteria that do the work.
- Check the size. A 10×15 cm cylinder does not fit every filter — measure the housing.
- Does not clear bacterial or algal cloudiness. Other products are needed for that.
- Do not replace all the media at once. Otherwise the filter loses its bacteria.
How biofiltration works
Fish excrete ammonia and food leftovers decompose — all of this is toxic. Beneficial bacteria on the sponge convert ammonia into nitrite and then into less dangerous nitrate, which is removed with water changes. To speed up the bacterial colony when starting a tank, bacterial products are used, for example Tetra Bactozym or Rikka Aqua Start.
How to clean the sponge
Rinse the sponge not under the tap but in a bucket of aquarium water drained during a water change: chlorinated tap water and hot water kill bacteria. Squeeze the sponge several times until the water is almost clear, and put it straight back into the filter. Detergents must not be used — the manufacturer says so explicitly. Clean it when the flow has noticeably dropped.
When to replace it
Even a durable sponge eventually crumbles and loses its springiness. If the filter holds several sponges, replace them one at a time a few weeks apart so the bacteria can colonise the new one. If there is only one sponge, you can first place the new one next to the old one and remove the old one later.
What to combine it with
A good setup is a coarse or medium sponge as the first stage, then bio-media and fine floss for clarity, such as JBL Symec. What else you need for an aquarium is covered in an aquarium for beginners: what to buy.
Less dirt, less cleaning
The more food leftovers, the faster the sponge clogs. Feed your fish as much as they eat in a couple of minutes and remove what is left. Tips are in aquarium fish food: how to feed.
Who it suits
The sponge suits aquarium owners with external and internal filters who need a spare or replacement medium-pore sponge. Other media and filters are in the fish equipment section.
Verdict
The Resun 35 ppi 10×15 cm sponge is medium-pore foam for mechanical and biological aquarium filtration: it fits external and internal filters, lasts more than a year and is cleaned without chemicals. The downsides are the inaccurate mention of anaerobic bacteria and the need to check in advance whether the size fits your filter.
FAQ
What does 35 ppi mean?
35 pores per inch — a medium pore size.
What size is the sponge?
A 10×15 cm cylinder.
Which filters does it fit?
External canister filters, internal filters and pumps with a sponge.
How do I clean it?
Squeeze it out in aquarium water, without detergents.
How long does it last?
Over a year, according to the manufacturer.
Can I trim it?
Yes, the foam cuts with scissors.
Can I replace the whole sponge at once?
It is better to replace it gradually to keep the bacteria.
