Yes and no. Most of the good bacteria is in the substrate, but it's also in your filter media (which is why most of us pack it with sponges, pads, and floss to increase surface area for the bacteria to reside), and a bit is on your decor. Packing the filter (if this is possible for your filter) and only vacuuming half the substrate at a time will keep the cycle without worrying about sucking up too much bacteria out of the substrate. Great question!
I'm just impatient over how long it's taking my tank to cycle and my goldfish is suffering too. But that's the subject of another post. (sigh)
packing the filter is intresting...is it possible on a marineland 12 tank?
Yep. I have that same tank and filter. I just buy filter pads and filter fluff and layer it on top of each other. I also took out the biowheel, which was useless because it kept stopping and drying out, and used that area to stuff filter media.
Hello Jackie. :;hi2Your good bacteria is found on all surface areas within your tank and filter. The largest quantities being in your filter and your substrate. I only suggest vacuuming 1/3 of the tank at a time to help prevent the tank from going into a mini cycle with increased ammonia levels. Ken