I think i will pass on this stuff ,i have another ? if you can help me,my water was very cloudy 4 or 5 days ago in the 2.5 so i put in a pen plax small world filter. It works really well and cleared up my water, the top half of this filter has carbon the bottom a sponge.These are meant to be thrown out and replaced,i read that these things could be opened and refilled ,so i picked up activated carbon today to try and refill it on the next water change ,and i plan to rinse the sponge part in tank water.So would this tank become cycled like this .If this does work i guess i would be cycling this small tank with him in it,and could transfer this sponge to the other tank.