Hi if its the same filter then you can just swap a sponge over yeah, if its not you can squeeze a mature sponge over the new ones to help seed them, I think this is what you mean?
As for new fish float them in the bag in the tank for 20/30 mins every 10 mins or so pour a little of the tanks water into the bag. When you are ready to release them submerge the bag and let them swim out don't tip them out. Leave the lights off for a hour and then when you put them back on give the tank a feed if there are other fish already in there.
Yes these fish are semi aggresive and as already said territorial as for the hiding under the bogwood this is normal too. If you wanted a fish that swam about in veiw all day Im afraid you you bought the wrong kind.
If you look at the picture on the boxes id say the main sheet slots into runners each side of the tank, with some sort of hooking device at the top - better check with the seller though, don't take my word for it.
Are all these ''women only'' insurance companies not just a gimmick then? I would have thought all insurance companies work on risk factors and the stats show that over all women make the least claims so the premiums should always be lower no matter who u insure with