Personally I think they are bad. They trap too much stuff, some of it good stuff like copepods. The bad stuff it catches, fish waste and food, sits in the socks and decays and ends up making the water worse if you don't change the socks out regularly (every 2 days tops). Too much of a pain to deal with IMO. If a person wants to use socks I would recommend using them just as a "weekend water polisher" type thing where you put them in on Saturday and take them out Sunday and run no sock the rest of the week.