I'm about to increase the surface area in one of my filters for biological bacteria colonies to grow, due to my intended increase in stocking for my 75gal. Over the last two years, I've been using ceramic media and Seachem Matrix, which is just porous rock. Matrix is supposed to accommodate more bio bacteria, due to its extensive surface area. According to Seachem, Matrix outperforms plastic bio-balls by about 170 times (ie - 1L of matrix = 170L of bio-balls). I don't know that there's really any truth to that. It could be clever advertising.

My recent thought is to begin using lava rock. I've read that it yields a great deal of surface area, due to how porous it is. I can tell you that Matrix is certainly not as porous as lava rock, so my thought is that lava rock probably outperforms it.

As mentioned, I have a mixture of bio-media in my tanks, using ceramic rings and the matrix, but I'm certainly not above trying something else. Lava rock is certainly more affordable and visually very porous. It's obvious to me that it can hold a great deal of bb.

Anyway, I just wanted to get the opinion of the community. I doubt that any of the options are a bad media to use, but if something can be more efficient than other options, I'd certainly prefer to use that.