Sponge Filter Question

[grump299]

I have started a 3.5 gallon acrylic tank with 1 betta for my wife. It come with a small filer I have packed with floss and media from my established tank for an instant cycle. Can I swap out the filter that come with the tank for a sponge filter and if so what size sponge and air pump should I use thinking of a dyi sponge filter. Thx in advance for the advice

 

[Platylover]

I’d be a bit concerned space wise by using an internal filter and not a HOB, but you can switch them. If the tank is already cycled you can leave the new filter in for a month with the old filter then remove the old filter. This way the new filter has adequate time to grow bb.