Ive had fishes for over a year and did start both with a fishless cycle. But this is my first buying everything with fish included. Over the next couple of weeks ill be purchasing a 55 gallon tank from someone who is going to be moving soon , included in the purchase is the filter, the lights, heater, gravel, decor, plants and all the fish living in it. When I move it over to my house I plan on keeping all of it but I do wish to change gravel to sand, so my question is if I should first set it up the same way , since it will be new water, keep it that way for about a week or so, then slowly change it out to sand so I don't mess up the cycle. Or can I start it off already half sand half gravel ?