DeLgAdO said:be careful with siporax and bio glass they have a lot of surface are and can becoem anarobic so have the water well filtered mechanically or you will have those rings producing toxic gases.
Howdy,
You are right that they will become anaerobic in parts. That, however, is positive, since it will contribute to the degradation of nitrate to gaseous nitrogen. But you are absolutely right that a good filter requires mechanical PLUS biological filtration.
I have to admit that I was not aware of Eheim Substrat Pro. Whereas Siporax is fine as 1 L media per 200 L tank volume, that ratio should be even better for the Eheim stuff. Question is, though, if the Eheim material has open porse like Siporax. If not, I would share DeLgAdO's concerns.
BTW: I brought my Siporax with me from Germany, I have no clue if it is available in the US. A quick Google search should answer that question.
HarleyK
it works great bro