You have the best possible situation, because the water and drain plumbing is already in one wall of that room. It is pretty easy to add water outlets in the bedroom, off the plumbing to the bathroom, and just a little harder to add a drain near the floor, off the bathroom drain. As long at the drain is close to the floor you can drain a lot of water flow with no problems. I suggest getting a plumber or a knowledgeable friend to run the pipes into the fishroom, with shut off valves on the water lines, but just an open drain with trap. Then you can use easy to install PVC to run water lines to the tanks for either a semi-automatic or automatic water change system, with the drain water going to the newly installed drain. You could put a "laundry sink", a plastic sink on the drain to make it even easier. While you are at it, if you buy a shower control valve, one of the type that holds the water temperature constant, that will let you set the incoming water at the correct temperature, easily. Then add a big, whole house filter on that line, with a solid carbon filter on it, and much of your chlorinated water problem is taken care of. It's the chance of a lifetime to really do a nice water system, easily.