How many sponge filters needed for a 20 gallon long?

[JenTheDroid]

I only have a Giant Betta (Not a king. Giants are bigger) and a snail. I’m not sure if I’ll ever get more since I’m sure the Betta is territorial now. I was using the Seachem Tidal 35 and I’m just not liking it. I have a double sponge filter but don’t really like the look. I wasn’t sure if a sponge filter is enough or I needed a HOB too, but if it is enough would it be better to get one large one in the middle or 2 smaller ones in the corner. I was also considering a box filter since I could add other media but if a sponge cleans pretty well then I’m good with just sponges. 

[Scapexghost]

One medium sponge filter should be perfect. Ideally in the middle but you could get away with putting it to the side

[HotTunaCartel]

I think as @Scapexghost said, a single medium would be fine.  

I just put this in two days ago (In a 20 long) and this is how much it has trapped with just a ziss airstone in the sponge 

Yes, I'm dealing with algae currently but kind of amazed at the difference between the medium and small sponge filters.  

 

[anewbie]

One is good enough but i prefer two in case there is some issue - like i need to qt a fish in a pail or something - then i can take one out and use it.

[quikv6]

I have a 20L with a bunch of pig....err....mollies and platies. I use 2 sponge medium sized filters in each back corner. I have one course sponge and one fine sponge...which seems to do quite a bit better visual job of mechanical filtration than when I had two course sponges. I like having the aeration/surface agitation on both corners of the tank.

[Streetwise]

With enough plants, this is a choice of flow, and visual impact.

[Flumpweesel]

Nothing to add about filtration but that is a very pretty betta and you never mentioned the mighty stature of your snail 🐌.  

Would you be able to sneak some bottom dwelling fish past your betta it's a lovely tank it be nice if something else could enjoy it.

[StevesFishTanks]

The cheapest and most powerful filter option for your tank and scenario would be the one you already own. The seachem tidal. I would put it on one corner and the sponge filter on the opposite side.