Have a 220 gallon with an fx5 and bough a bag of lava rock and it was all the black rock. Have been having a problem cycling the tank the nitrites leveled out and the tank cycled I took 30 gallons out and now it's cycling again went and talked to the owner of my lfs and he said he never had luck with dark lava rock only the red ever worked for him he has several huge ponds behind the store with 55 gallon drums filled with the red lava rock for filtration and he swears by it. Anyone have any imput on the dark vs light lava rock or what else I could use to get the tank to hold some bacteria it is a bare bottom I was thinking about adding gavel
