If you are going to quarantine the fish I don't think you will need to do the dip. but if you do dip it, don't use the methanynol blue or at least I wouldn't. it is pretty hard to get the correct dose for a dip. Oh and you would want to dip it prior to putting it in your quarantine tank if you were going to do it. I think it will cause un needed stress. Be careful how much and how often you feed on your quarantine tank. Its very easy to have ammonia spikes in a bare tank with a very small biological filter. just my 2 cents