Is the use of LR Rubble something new
I am not sure just how new this trend is. LR
rubble is a better filter media then bioballs. They do a better job at removing nitrate from the water. If you are having trouble with nitrates, this could be part of the problem. Can you list your current livestock, your feeding scheule and the type of substrate you have? What are your current NO3
What about in a hang on the back filter?
It is really up to you. HOB
filters add flow tothe tank and provide you with a place to run chemical filtration. They also provide mechanical filtration. Some will also provide biological filtration, but once the filter pad is changed you llose the bacteria that is on it. You can remove everything from the filter and fill it with LR
rubble if you want. IMO
filters do okay provided you have plenty of LR
in the main tank for consistant biological filtration.