I'm turning my aquarium upside down and making a different set up. My small question is : should I be using the old water from my aquarium or new ones or only part of it? in terms of algae, diseases, etc.
Egad, how on earth are you able to keep Silver Dollars and plants like that together?? My SD's mow nearly everything down unless I overwhelm them with plants that are tough first....
Yes, you are on the right track keeping your filter media and any other thing that may have bacteria built up on it. Saving the old water isn't necessary unless the new water will be much different from the old. Just be sure to keep your filter media, substrate, plants and ornaments moist while you're making the change.
You say "turn my tank upside down", to me this means starting over. Why would you want to start over? Why not just garden within your current set up? Pull out the plants that you are tired of and plant new ones. I think it is better to make smaller changes over several weeks than to start over.
Thanks everybody for your replies.
JanS, I managed to keep the silvers from the time they were little. They grew up and started mowing my plants : a potamogeton was cleared of the aquarium over night. I returned them to the lfs.
Jeff Kropp, the reason I'm turning it upside down is my un-inert gravel and not so good substrate I had from the start. It's not so favorable but I have no choice.
In the case of new substrate, you will want to inoculate the bottom layer with mulm from a healthy tank. Getting the bacterial life started in a new substrate is considered by many to be a key componant of success. The water is much less important. If you had very delicate or rare fish you might want to use 50% old water to ease their transition. Plants are much less delicate.
To concentrate your mulm put it in a tall narrow container and let settle. You will then be able to siphon off the clear water above the mulm. After you have concentrated the mulm you then dump it into your empty tank before adding substrate. In this way you can accelerate your transition towards a mature tank.