Seeding new filter

[giffmastaflex]

Last Thursday I put a sponge filter in my 55 gal to seed for my 20 gal. How long will it take for the sponge to gain the BB? I was hopping to set it up tomorrow and putting about 5-10 gallons of water from the 55 into the 20 as well. Would this be ok to add fish?

 

[Greta1981]

It will take at the minimum a few weeks for good bacteria to grow on the sponge. Water carries little to no BB, so that won't help with speeding up the cycling. Add a few tablespoons of your used substrate to the new tank and that will help start the cycle even without the filter. That said, it will still take time for the cycle to establish itself in the 20. I would not recommend adding fish yet/