To establish new sponges there is a simple technique. Set up the tank including the sponges. When you go to clean the media in other tanks, rinse some of the media in the new tank with the sponges. In short order much of the squeezings will be inside the sponges and the rest settled onto/into the substrate. After that you need to add ammonia. Dose the tank to 2 ppm. When you can test 0 ammonia, check for nitrite. If this is 2 ppm or less, add the same dose pf ammonia as the first time and test in 24 hours. If he ammonia is 0, as soon as the nitrite is 0. stock the tank after doing a big water change.
If you are using Safe Start you can follow the same process. Within 5-7 days the tank should be ready for a full stocking level. It can go faster in some tanks. It depends on how much Safe start you add. Bear in mind it is live bacteria that is dormant. Ammonia and nitrite wake it up. However, because it should contain enough nitrite oxidizers to handle what ever the ammonia ones make, you may never get a nitrite reading. Once the tank zeros out 2 ppm of ammonia in under 24, you are good to go with a full stocking.
