The less you mess with your water the better things will be for you and your fish. A varying pH value will make for sick fish very quickly. Most reticulated (tap)water is OK for the vast majority of fish species. All you should need to do is make sure that when you first set up the aquarium and when you do large water changes, any Chlorine is either chemically neutralised by adding a "conditioner" or allowed to evaporate off. If you are having pH variations in an already established tank, you could use a pH stabiliser block/buffer. These are fairly cheap and should keep the water around pH7. I believe there are also various different blocks available that will actually adjust the water to suit both Alkaline and Acid loving fish too.
Use the forearms
Use the forearms
oak
Fake Coral
No. You should use aquarium salt, sold at pet stores.
The "brown stuff" should not be a disease, it's called algae. To get rid of this, move your aquarium away from sunlight and make sure those plants are safe for aquarium use. If you can't move the aquarium away from sunlight, use some medications for your fish tank at your local fish store.
Progress in the main storyline until you reach North Coast of Canada, after completing this part of the quest, the aquarium should be open for use.
I would use 4"x 3" timbers.
Anything labeled safe for aquarium use. Beyond that, it depends on what type of fish you are keeping, and whether or not you have plants, for which type of aquarium substrate (gravel or other lining for the bottom) should be used.
oksigen
with the use of acetone
If they are in a pond, then having trees that are taller away from the pond should help. If they are in an aquarium, you should use a surge protector