Hi, I'm currently using a 3-way hang-on filter which consists of a sponge, activated carbons & bio-balls. I was told that the bio-balls is to killed off any harmful bacteria. Is that sufficient? Also, how frequent do I need to take out the filter for cleaning & replacing the carbons? Pls advise.
Does that mean while changing the 20% water, I will leave the fish inside the tank? Thx.