Okay I will start off with saying I've always added my dechlorinator after the water change and have never had any problems. However, I've recently set up a 29g with 2 sponge filters as my filters. I've grown concerned during my python water change of this tank in particular, is it okay to still do a water change then fill up with my python then after dose with my prime? What I'm afraid of is the tap water killing the sponges BB. I've never worried about this before since the filter media on my other tanks are all out of the water.