i have had my 75 gallon aquarium for eight years.. a week ago i converted it to a saltwater tank but kept my same bio wheel filtration. i am using puka shell substrate..right now i only have 4 electric blue damsels in it. it is a fish only tank. i hope to get some clown fish and green chromis whenever the cycling process is complete. i put bio spira in when i converted to a saltwater tank..it was only cloudy for one day so i really dont know if it is cycling or not.