It's an 8g biocube. I change no more then 2g's every friday. I start the water thursday night, test the sg/cal/ph before I add it to the tank. I've got 5 and 1/2lbs of LR in the tank, with about 1lb of LR rubble in 2nd chamber along with 16oz bag of Chemipure Elite. 1st chamber is factory made filter. I switch up between that and just floss. To much info? LOL.