Hi all, In the last TAG I enjoyed reading Takashi Amano's article "Possibilities of Sozo Haishoku". It was actually interesting to know that this guy actually battles algae on a daily basis.... :-) But one thing that he said is "news" for me - He said that there's a time limit for an aquarium and at some point one has to replace the substrate and "renew" the tank. I thought that a reasonable substrate runs out of nutrients (except iron) in about a year or so however it should still absorb some nutrients from the water and my impression was that water column is the king as far as fertilization so no need to care so much about substrate anyway. Am I missing something? Aviel. _______________________________________________ AGA-Member mailing list AGA-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/aga-member