How to Clean a Fish Tank...

Step 5 Get rid of the water...

You have to do something with the dirty fish water. I use it to fertilize my plants. Whenever my water collection container gets full, I pull the siphon out of the water and take the container outside, pour the fish water on a plant or into my compost bin, and then repeat the whole process until the majority of the water in the tank is gone. I normally leave about a inch of water before I refill the tank. When it is a very hard to get the siphon going if there is a small amount of water left in the tank. It will be so diluted when the tank is refilled, that it really won't make a big difference in the end cleanliness of your tank.