Lava rocks

[Anna94]

I would like to completely switch from Matrix to lava rocks, but I don’t want to do it all at once and lose my cycle so can I replace half the Matrix with the lava rocks and then after maybe a month replace the rest?

 

[Autumnsky]

Are you meaning replace the Matrix within a filter to lava rocks in the filter, or lava rocks as decoration and BB colony in the tank?

Matrix would have much more surface for the BB colony in the filter.