Hey guys. I'm kinda new to this, don't know a whole lot about it. I currently own a 29 gallon aquarium. With various types of tetras. However I recently decided to give all of my tetras away to a friend of mine, as I would now like to do a goldfish setup instead. I now have an empty aquarium, all of the decorations/plants have been removed. I now have 8 corydoras and 1 pleco remaining in the tank, which I did not give away when I gave all of my tetras away. When I had my tetras, there was a big piece of wood in my aquarium, which caused the water to turn brownish, tea like. But as I mentioned before, the wood, along with all of the other decorations, have now been removed. So I have a few questions... #1 how do I go about doing this massive switch from a tropical fish tank to a goldfish setup? #2 should I do a few water change cycles before adding goldfish, also to help clear up the tea like tint in the water? #3 must I change all of the filter media and clean out the insides of the filter? #4 must I wipe down the glass? #5 can my corydoras live with the goldfish that I will be getting in the near future? #6 do my corydoras need a heater to survive or will they be fine in room temperature water along with the goldfish?