I have a 20 gal tank that I have just removed the fish from, I removed most of the plants. I'm left with 2 crypts and java moss on the side panel and across the back panel of the tank. I'm not sure when I am going to put fish back in. I am moving this weekend and will refill with water and leave the filters running. what if any nutrients will I need to supply the moss and how often? thanks -linda