I'm not sure what you would be starting over, but I don't think that's necessary in any case. You have the sponges, which is great, and biobags too? Great. You're already well on your way then!
If you're uncertain that your cycling is complete or not, it's really easy to find out. If you haven't done so already, it's imperative that you invest in an Ammonia, Nitrite and Nitrate test kit. You can get one from API for about 25-30 dollars.
To know that your tank is fully cycled, your Ammonia should be 0 (or very close), your NitrIte should be 0 (or very close), and your NitrAte should be between 10-20. This will indicate that your bacterial colonies have grown to be able to consume all the Ammonia, change it into NitrIte, and then NitrIte into NitrAte.
If your any of your parameters are high, then that's bad news for your fish and you'll want to do a partial water change (PWC). For your tank and your current stock, you'll want to do about a 15-20 Gallon change every day until you can get your levels down. When your levels stop rising, then you can ease off the frequency of your PWCs.
These water changes won't hurt your fish, so long as you use a dechlorinator for all the water you put back in. I use AquaSafe, myself. And try to make sure the new water is about the same temperature as the water in your tank.